Experience
in a Book
Air
Conditioner/Heater
SYSTEM TYPES: Despite many minor revisions, the
basic air conditioning and heating system in the XJ-S
remained essentially unchanged until 1987. In 1987, the
entire interior system was replaced with a new design,
commonly referred to as the Delanair MkIII. The earlier unit
within the dash was a sheet metal assembly painted with
gloss black paint, while the later system is largely
plastic. The earlier unit was controlled by a single servo
assembly via a conglomeration of linkages within the right
side of the console, while the Delanair uses multiple local
servos and controls.
The compressor and freon circuit is essentially common to
both systems, as are a few other things. Within the dash,
however, the two systems are totally different. So, the
following discussion is divided into three sections: Things
that are common to all systems, things that pertain to the
pre-1987 system only, and things that pertain to the
Delanair MkIII system only.
Common
Features
AIR CONDITIONER COMPRESSOR: Up through 1992, the
Jaguar A/C compressor was labelled "Harrison" but was in
fact the standard GM item referred to as an A-6 -- and
therefore comparatively cheap to replace. In fact, it is
generally recommended to simply replace the compressor
rather than attempt even the simplest repairs. After a few
years, the O-rings start to fail, and each time you correct
a leak you must have the system evacuated and recharged.
With the current regulations on R-12 refrigerant, the cost
of a single charge can exceed the cost of the compressor. If
you are having the system recharged anyway and the
compressor is more than seven or eight years old, it might
be wise to simply replace it even when it is still working
fine.
Although you can find an A-6 compressor really
cheap, Randy Wilson says, "The compressors should be good
for many years. Continuous failures are not the fault
of them being rebuilt units. It's the fault of them being
cheap quasi-rebuilt units. This is a fairly major problem we
fight in the auto industry.
"I can buy these A-6 compressors from a local distributor
for $49 per unit in very small lots... with no core return.
These units, I can tell you from experience, have an average
life expectancy of around a month. Many fail the first day.
I have found a rebuilt compressor that I like. It's a
lot more expensive. But I haven't had one of them
fail yet."
The threads on the replacement compressor are likely to
differ, in which case you will have to replace the mounting
bolts. In particular, the two mounting bolts at the bottom
rear and the long bolt that holds the inlet and outlet
connections in place are 10mm on the original, and will
probably have to be replaced with 3/8" bolts (either fine or
coarse, they vary) when installing a replacement. 3/8" is
only slightly smaller than 10mm, so sleeving will not be
necessary. Also, the small front mounting bolts as well as
the bolt that holds the fuse assembly may have to be
replaced.
The new A-6 compressor also may not fit the protection
switch that was in the original compressor. Read the section
below.
From 1993 on, a Sanden (Japanese) compressor was used.
While many may bemoan the discontinuation of the excellent
A-6, the Sanden likewise has an excellent reputation among
A/C mechanics.
COMPRESSOR PROTECTION CIRCUIT -- A-6: Just below
the inlet and outlet connections on the A-6 compressor is a
sensor held in place with a C-clip, with a wire connected to
it. On the 1983 XJ-S, this is a thermally-operated switch
that shorts to ground in the event that there is trouble
with the freon system. The shorting causes a resistor within
a three-connector fuse assembly to heat up, which in turn
causes a fuse to melt, breaking power to the clutch and
disengaging the compressor. This is a common arrangement on
GM vehicles, and the fuse assembly is readily available. The
fuse is usually attached to a mounting hole on the
compressor itself.
Do not connect the fuse backwards. There is a
little tang on the center connector that is intended to
indicate which way the plug goes, but it's not very
foolproof. If you install it backwards, the clutch will not
engage and the fuse will blow immediately.
A replacement compressor is likely to have an aluminum
blank-off plug in place of the fault sensor. It is probable
that you cannot install the thermal type sensor in place of
the plug because there has to be a suitable opening
underneath the plug for the tip of the sensor, and there
often isn't. However, the sensor wire can just be left
disconnected and the system will work fine -- there just
won't be any protection for the compressor if the system
loses freon. In fact, it is just as well to remove the fuse
assembly as well and run the power wire directly to the
compressor clutch. Since the standard procedure is to
replace the compressor in the event of freon loss anyway,
this may be acceptable.
There is a second type of protection switch available: a
pressure-operated switch that supplies a ground to the
compressor clutch when the freon circuit pressure is normal.
This second type is the best to use; the early system with
the thermal fuse is temperamental at best. The pressure
switch has a plastic body, as opposed to the thermal type
which has a metal body with a heat probe protruding into the
compressor. Since the pressure sensor has no protruding
probe, it can be installed in a replacement compressor in
place of the aluminum blank-off plug. According to Stefan
Schulz, Jaguars began being fitted with this type from the
factory in the mid-80's.
Note that the thermal type switch is normally open and
connects to ground in the event of trouble, while the
pressure type is normally connected to ground and opens in
the event of trouble. To use the pressure type protection
switch, modify the harness so the power goes straight to the
clutch and the ground terminal of the clutch is wired to the
pressure switch; a three-connector fuse is not needed.
AIR CONDITIONER COMPRESSOR
FRONT BRACKET -- A-6: The front end of the A/C
compressor is supported by a plate bolted to the front of
the timing cover. This plate is not symmetrical; it
goes in only one way. If you put it in backwards, your
compressor pulley won't line up right with the belt. To be
safe, mark the plate before removal.
AIR CONDITIONER COMPRESSOR -- MOVING OUTTA YOUR
WAY: Many jobs, such as changing spark plugs or pulling
the cam covers, requires moving the compressor a little bit
without removing it entirely or disconnecting the freon
lines. Several people, including Victor Naumann and Harry
Trafford, have pointed out that a block of wood positioned
between the V and the top of the radiator can be very
helpful to hold the compressor forward and above its normal
position while you're working.
AIR CONDITIONER COMPRESSOR -- REMOVAL AND REFITTING --
A-6: In order to correct for tolerance in dimensions
such as the overall length of the compressor, the holes in
the rear compressor support where it is bolted to the valley
cover are very slightly slotted, so the rear support can be
slid back and forth a bit and then the bolts tightened down.
So, whenever the compressor is replaced with a different one
or the valley cover has been removed, the proper way to
reassemble would be to leave these two bolts loose until the
compressor is in place and the bolts at the back end and all
four bolts in the front support plate are tight, then
tighten the two bolts holding the bracket to the valley
cover last.
When you are not fiddling with the valley cover bolts or
replacing the compressor with a different one, lifting and
reinstalling the compressor without loosening those bolts
seems to work well enough if you do things in the right
order. Always loosen the two bolts that attach the front
mounting plate to the timing cover before lifting the
compressor out. During assembly, always have all four bolts
at the front (two holding the plate to the timing cover, two
holding the compressor to the plate) in place but loose
while tightening the bolts in the rear support. Be sure to
reconnect the ground wire.
As in most cars, the compressor is connected with
flexible hoses. This enables some movement of the compressor
for such jobs as replacing the spark plugs without
disturbing the freon system.
FILTER/DRYER: Apparently, the receiver drier unit
on some Jags has O-ring fittings; on other Jags, the unit
has flared fittings on it. Either drier should be readily
available, it is not a special Jaguar part. Be sure to
install the replacement in the correct direction (they
always have flow direction arrows on them); the location of
the sight glass may not be a good indicator, since there are
reports of the sight glass being on either the left or right
side.
EXPANSION VALVE: The expansion valve on this
system (at least on the '83) is fairly standard; if you look
through an A/C shop's parts book you will find there are
several interchangeable part numbers, including some from
Jap cars. But further, there are several other part numbers
that represent similar expansion valves except that the
capillary tube and/or sensor tube are different lengths. The
expansion valve called out for the XJ-S has very short
tubes, since the places they go are only a couple inches
away. But it still may be beneficial to get an expansion
valve with longer tubes just to make it easier to
install.
Also, some of the expansion valves have the capillary
tube attached on different sides or at different angles.
Selecting the optimum arrangement here can also ease
installation considerably.
The sensor tube has a little coil on the end that must be
installed against the pipe coming out of the evaporator, and
must have some insulation put over it, so that it senses the
temperature of that pipe. On most cars, this coil is merely
strapped to the pipe with a tar-like stuff. However, on the
XJ-S there is actually a little boss built onto the
evaporator outlet fitting just for this coil. Once you get
the old tar stuff off, you must loosen two Phillips screws
to get the old coil to slide out.
REFRIGERANT LEAKS: Michael Minglin says, "A
possible solution is a refrigerant additive available from
Cryo-Chem Int'l at 1-800-237-4001. It is called Cryo-Silane
and reportedly seals small refrigerant leaks, without
clogging the system. It is guaranteed to seal and hold for
one year any a/c system that takes longer than six hours to
leak down. As I said I have not yet tried it, and it isn't
cheap, but this may be the answer to small hard to find
leaks.
"On the matter of hard to find leaks, with the a/c
service gauges hooked up it is impossible to find leaks in
the service ports or valves. If your mechanic cannot clearly
show you the leak, have him disconnect his service gauges
and check the the service port valves before starting to
change out expensive hoses and parts."
LEAKY SCHRADER VALVES: The guy who works on my A/C
for me has a tool for replacing the Schrader valve without
discharging the system! It screws onto the fitting, then
allows you to unscrew the valve from the fitting within a
glass housing so nothing leaks out. Put a new valve in,
problem solved. Only a little squirt of freon is lost when
you remove the tool, the amount that filled the volume of
the tool itself.
FREON REPLACEMENT: R-12 is soon to be history, and
many XJ-S owners are concerned about what they will have to
do when they can no longer get their freon circuit
recharged.
One possibility, and the first to be "approved", is to
modify the system to use R-134a refrigerant. Jaguar offers a
retrofit kit; the part number is JLM 11610 for the 1993-94
XJ-S with a Sanden 709 compressor, and JLM 11611 for the
1979-92 cars with the Harrison compressor. To quote from
Technical Service Bulletin #8239: "The primary changes
involve the replacement of the existing compressor
lubricating oil with an oil compatible with both HFC R-134a
refrigerant and with the residual R-12 lubricating oil. It
is not possible to completely flush R-12 type lubricating
oil from the refrigerant system prior to changing to Ester
oil and R-134a. Additionally it is necessary to replace the
input shaft seal of the compressor with a seal compatible
with the R-134a refrigerant and oil." Note that the use of
R-134a refrigerant reduces the cooling capability of the
system somewhat.
Perhaps a better choice is R-406a, which has now been
approved for automotive use. More expensive than R-134a, but
is not only a drop-in replacement for R-12, it also
increases the capacity of the system by a few
percent. There is more info available on the WWW at
http://www.worldserver.com/r406a/
and any search of the WWW is likely to turn up a flurry of
information on R-12 substitutes. Or call McMullen Oil at
1-800-669-5730 or Monroe Air Tech at 1-800-424-3836.
Other possibilities include a host of up-and-coming
substitute refrigerants such as Hot-Shot or GHG-X4 (GHG in
honor of the chemist who put the formula together, George H.
Goble), supposedly direct replacements for R-12 with little
or no conversion necessary.
There are also folks who have figured out how to charge
the system with a mixture of propane and butane. This is not
recommended, however.
Michael Minglin found a page on the WWW "for those of you
who would like to be able to purchase R-12, R-134a, or just
about any other kind of coolant, to do your own A/C repairs:
http://www.epatest.com
"At this website you can download the EPA section 609
manual free, take the test online for under $10, and print
out an instant temporary EPA certification certificate, if
you pass the test. The actual certification card is mailed
in about 30 days."
HOSES: Most A/C shops claim to be able to rebuild
hoses. It turns out that some hoses are more difficult to
rebuild than others, and the more difficult ones require a
special crimp tool that, while reasonably priced as shop
tools go (no power, hand operated), was only introduced
relatively recently. If the A/C shop is dealing with the
older crimp tools, it cannot rebuild some hoses. The usual
result is that they will cut the fittings on your old hose
and braze on sections of tubing that their tools can fit a
hose to. This looks like c__p when done, but does work.
If the fittings on your hoses happen to be aluminum,
only the newer tool will work, since brazing is out
and the older tool will crush the tube.
Now, does any of this apply to the Jaguar? Well, probably
not mine; it appears to have standardized fittings made of
steel, so perhaps the older crimp tool will work. But I
dunno what fittings are used on other Jaguars, so I thought
I should clarify the situation. I have mid-80's Hondas that
have unique, aluminum fittings on the hoses; a shop with the
new crimp tool can rebuild, a shop without it will tell you
that the hose is unrepairable and you must buy a new one
from Honda. If the newer Jags have similar developments,
take note.
WINDSHIELD FOGGING: If your windshield fogs up
more than it should, the first thing to do is determine if
the fogging is on the inside or the outside -- wipe your
finger on it, or turn on the wipers. If it's on the outside,
the problem is that your air conditioner is pumping very
cold air through the defroster vents, chilling the glass and
causing condensation on the outside. There are two major
causes here:
First, the flap that is supposed to close off the
defroster vents is not closing properly, or the sealing foam
on the surface of the vent has rotted away. On the pre-1987
systems, the flap is operated by a vacuum capsule
immediately to the left of the glovebox (left hand drive
cars), to the right of the center facia vent, but it's
really difficult to get to without pulling the dash. The
flap itself is basically impossible to work on without a
total disassembly of the dash, including purging the freon
system and pulling out the entire A/C assembly. Sometimes
the problem is the hinge the flap moves on, a cheap plastic
item that should be replaced with something more substantial
if you ever have the opportunity.
Fortunately, the second cause is more common (on the
pre-1987 system, anyway): the linkage controlling the entire
A/C system is misadjusted, causing the air coming through
the upper half of the system to be colder than it should be.
Readjust the control linkage.
If the fog is on the inside of the windshield, it is
usually due to one of two causes: either the condensate
drains are plugged up causing the system to fill with water,
or the heater core has sprung a leak. To determine which,
John Shuck sends this tip: "This sounds crude, but wet your
finger and touch the window. Taste your finger now. If it
tastes sweet, that's antifreeze that's coming from guess
where....heater core."
CONDENSATE DRAINS: All air conditioning systems
must have a condensate drain to drain the water that
condenses when the air is cooled. The XJ-S has two -- small
plastic tubes protruding downward and ending well above the
exhaust system on either side of the transmission. When
working properly, these tubes will be dripping water on the
exhaust pipes during muggy weather. However, when the lines
plug up, the water fills up inside the A/C system, causing
wet spots on the carpet, reduced airflow, etc. It will
sometimes dump water on the driver's or passenger's feet
when cornering. It also appears to be the culprit in a
strong tendency to fog up the windshield immediately upon
starting the car after it was recently shut off.
From under the car, run a piece of stiff wire up through
each of the tubes until it goes all the way into the A/C
unit. Compressed air might also work. Since Jaguar made
these tubes entirely too small (they are twice this diameter
on most cars) they get plugged easily and need to be opened
up regularly.
If your drains are plugged beyond this simple repair,
Hunt Dabney provides a description of more serious work:
"Remove the side panels from either side of the transmission
tunnel (the ones that have the vents in them). On the left
side, if you look at the front-most ëcorner', all the
way to the left when viewed from the side, you should see a
rubber reducing nipple attached to the lower portion of the
compartment containing the A/C coils. This has a piece of
3/8" poly tubing protruding from the bottom, down and
through a grommet which passes through the top of the
transmission tunnel. This one is easy to get to and remove.
To replace, use new hose clamps, and possibly silicone seal
if the grommet has problems (or a new grommet).
"Above this point is a duct, about 4" in diameter and
which extends under the dash from the heater a/c unit to the
left side dash vents. By rotating the end a bit ccw, it may
be withdrawn from the heater box. This will allow you to
look in the box and inspect for dust and debris. Clean out
through here if you can.
"The right side is very similar, but the A/C servo
linkages may get in the way and require removal. In fact, it
may be necessary to remove the servo unit. Getting in
through the duct, as previously described, is workable, but
you have to remove the glove box."
According to Larry Lee, the drains may be getting plugged
with bits of the foam insulation used in the system; being
British non-metallic material, it rots and falls into the
drains. The insulation itself is not worth replacing unless
you're doing other major work, because it requires tearing
the dash and A/C system apart.
Note that Technical Service Bulletin #8218 describes a
problem with the condensate drains after the airbags were
introduced in 1989 and up to VIN 165565. Apparently a
revision of the A/C system was necessary, and as a result
excess sealant on the drain separator plate may plug the
drains. After VIN 165565, the sealing was omitted. Later,
after VIN 168340, an additional hole was provided in the
separator plate.
PLUGGED CONDENSATE DRAINS -- PREVENTING SECONDARY
DAMAGE: Hunt Dabney says, "Last time the drain tubes
clogged up on mine, it dumped quite a bit of water over the
servo and ruined the feedback pot. I made a mylar shield to
prevent this from happening again. I took a sheet of 6mil
mylar (used to use for PC board layout before CAD), cut it
so that it would fold over the servo assy from the mounting
surface side, with tabs folding over the corners and
openings where required to clear the operating levers, cable
and tubing. Then, crease the folds, install over the servo
and reinstall the servo cover. I cut an opening where the
foam "friction" piece that pads between the servo and the
mounting surface go, so that it would not slide due to the
mylar."
See also the note on the official
Jaguar protection for the stereo.
HEATER CONTROL VALVE: The
Jaguar heater control valve is a vacuum-operated pot metal
contraption located in the dead center of the firewall,
under the rear loop of the fuel rail. It consists of a metal
cylinder with a hole through it within a ported housing; the
cylinder is rotated to align the hole with the ports to
allow flow, and rotated so the ports face the blank sides of
the cylinder for shutoff. This valve is expensive, difficult
to get at, and prone to corrosion and seizing.
Note that a heater valve should provide a total 100%
shutoff of water when vacuum is applied; if it is leaking
when closed, even slightly, it introduces quite a lot of
heat into the climate control system when it is supposed to
be in full cool mode. While the supply air from the vents
may still seem cool thanks to the operation of the flaps
bypassing the heater core, the system won't work as
efficiently as it should. When in doubt, test it; connect
the valve to a 5/8" garden hose with a hose clamp, turn on
the water faucet, and suck on the vacuum line with your
mouth. If the flow doesn't completely shut off, you need a
new valve.
It's a fairly simple matter to remove the intake manifold
crossover pipe, and doing so may provide vastly improved
access. On the '83 XJ-S, the mount bracket is held to the
firewall with two bolts that thread into nuts welded onto
the firewall. However, Michael Bain reports that some models
use nylon nuts within the wiper motor area. In this case, it
may be easier to remove the intake grille/wiper motor
assembly and unbolt the heater control valve from the back
side, but if the nuts aren't nylon you won't get anywhere
going that route.
Do not simply eliminate the valve and plug the hoses. The
hot water supply is necessary for proper operation of the
climate control system, even when it's in cooling mode. A
temperature sensor in the heater core will limit the blower
operation if the water isn't warm enough.
When the Jaguar valve causes problems, whatever you do,
don't replace it with another valve just like it! That metal
thing is junk. One better option would be to take it to an
auto parts shop or auto A/C shop and ask for a Chevy valve
that has 5/8" hose connections. The Chevy valve is a
butterfly type and is made of plastic and stainless steel,
and weighs so little that it doesn't need to be mounted; it
can merely be suspended in the hose. It also costs only
about $20. Make sure the valve you buy is normally open, and
applying vacuum closes it. With a little hose rerouting, one
of these valves can be located at the right rear corner of
the engine compartment where it's easy to get at.
Unfortunately, the Chevy valves are not that great
either; the shaft is stainless but the butterfly itself is
rubber over a basic steel disk, and the steel rusts and
blisters the rubber off, causing it to leak when shut. Oh,
well, at least it's cheap.
A better option yet is to go into an auto parts store and
ask for a heater valve for a Jaguar. Some stores will stock
the original, but other places -- notably the cheaper places
-- will hand you a generic heater valve made by Factory Air,
part no. 74803. This valve is made almost entirely of
plastic, and costs only about $10. Although some people
don't like plastic, the design of this valve is so superior
that it is undoubtedly the most reliable choice. This is a
domed poppet valve rather than a rotating-cylinder valve
like the Jaguar original or a butterfly like the Chevy
valve, so the reliability of a total shutoff when closed is
much better than either. Discount Auto Parts and Pep Boys
sell this valve, and they always seem to have it in
stock.
Note that the vacuum hose in the XJ-S is 1/8" while the
connection on the Factory Air valve is 1/4". You will
probably not want to try to stretch a 1/8" vacuum hose over
a 1/4" connection, so plan accordingly and buy an adaptor
and a short piece of 1/4" vacuum hose while you're in the
store.
BLOWER FANS: The XJ-S uses two fans, one on each
side. Therefore, there is one more failure mode possible
than on other cars. If your A/C is putting out cold air but
doesn't seem able to cool the car, check that both fans are
working. If one runs and the other doesn't, the system
appears to be working but capacity is severely reduced.
Since both fans feed a common plenum, failure of one fan
reduces airflow at all outlets but does not affect one
outlet more than another. When both fans are working,
airflow is quite forceful indeed at high speed, and cooling
should be more than adequate.
VACUUM: The control system relies on a supply of
vacuum from the engine, and stored in a reservoir. As Tom
Wagner discovered, it pays to make sure the supply is
working before troubleshooting the rest of the control
system. There is a check valve in the line to allow the
reservoir to hold vacuum when the throttle is opened, and
this check valve stuck shut -- preventing either the
reservoir or the control system from getting any vacuum.
VACUUM CHECK VALVE: One might expect that the
normal failure of the vacuum check valve is that it fails
open, but Mike Morrin had the opposite problem. "My A/C
system has always had marginal performance of the vacuum
actuators, with the heater valve (new) and centre vent flaps
always slow to operate. I got tired of the centre vent
taking 5 to 20 minutes to open.
"Tonight I decided to check the vacuum non-return valve,
which seemed to be working. While trying to decide what to
do next, I was sucking on the non-return valve, and it
occurred to me that I was sucking rather hard before any air
got through.
"On impulse I tried to pull the valve apart to see what
was inside, but it was too tight (or glued together). I then
poked a piece of steel wire in the end where the air goes
in, and there was a small click. That must have been the
rubber thingy unsticking from its seat, because the valve is
now much easier to suck through (but only one way). After
refitting, all the vacuum actuators are now working like
clockwork.
"That is the easiest repair this week.
"The XJ-S help book mentions that these valves sometimes
block up completely, but this was only partial, and seems to
have been fixed by a poke in the eye with a blunt
stick."
CENTER VENT: The center dash vent on most XJ-S's
has three sections: a section on the left and right ends
that can be adjusted to aim where desired, and a center
section with no adjustability that simply blows straight
rearward. Here in Florida where the weather is both hot
and humid, this center portion can blow enough cold
air straight back to cause the rear windshield to fog up --
which is a real pain, because the rear window defroster has
a timer and won't stay on indefinitely, you have to keep
turning it on and off to maintain visibility in the mirror!
Those who don't have fogging problems still dislike that
center vent blowing air to the rear, since only sadists ask
anyone to actually sit in that rear seat. Peter Cohen
confesses, "Over the years, I have developed the unconscious
habit of driving with my elbow resting on the console, arm
up, and my hand positioned as a diverter to direct the cool
air toward me."
Emile A. Des Roches suggests two possible fixes: "The
Cheap Solution -- Lift off the surrounding wood (gently);
the plastic vent will come out with gentle even pressure.
Cut a piece of relatively stiff black cardboard to the
height of the inside (towards inside of dash) vent and to a
width roughly 2" narrower than the width of the center vent.
Place same (black side facing cockpit) in the vent and
reassemble. This solution performs the same function as
resting one's hand in the air to divert air towards the
driver and is far more sanitary."
This author made a similar modification to his center
vent, except he used black plastic instead of cardboard and
shaped it into a V so it would more definitely deflect the
air to the sides. Using the simple flat piece may cause more
blockage rather than deflection -- which may be desirable
since it would result in more air flowing out all the other
vents.
To all this, Franck Guilloteau adds: "While my car is an
'85, the wood trim is in immaculate condition and I found
that after several unsuccessful tries it wasn't worth the
risk of breaking or chipping the trim. I resorted to an
alternative method of removing the two directional vents of
the main center vent. A small screwdriver, X-acto blade and
minimum dexterity will do the job in five minutes.
Directional vents have a small leaf spring that increase the
friction and hold them in place; it can be pushed out prior
to removing the vent. These openings allowed me to slide
black cardboard (or plexiglass covered with black felt in my
case) and wedge it in place from behind. All told a really
"cool" mod."
Des Roches continues: "The More Problematic Solution --
Replace the center vent with one from a very late XJS. At
some point after 1993, the center vent design with moveable
vanes at the edges and fixed vents at center was replaced
with a design that consists of two (no space between)
adjustable vents. This is a direct (no trimming) replacement
for the earlier unit which presumably could be obtained from
either Jaguar spares or a wrecking yard." Dean Gosselin adds
that the part part no. is BEC-26361.
Dan Jensen adds, "I changed out the center vent on my
XJ-S... It makes a dramatic difference in the amount of cold
air that can be directed over the driver and/or passenger. I
would offer one additional note to the installation
instructions. While the replacement vent has the same width
and height as the original in my car, it was approximately
1/8 in. deeper. The extra depth resulted in the vent face
extending out a comparable distance from the metal dashboard
and prevented the wood fascia from sitting firmly against
the dash. As a result, I had to get out a wood rasp and file
off 1/8 in. around the inner perimeter of the vent. This
took about 15-20 minutes, including the time needed to get
all the little specs of plastic off the louvers when I was
finished. In addition, it was necessary to file two small
central notches in the metal dash to accommodate two added
bulges in the new vent. This took no more than a minute or
two with small round file."
Samuel Louw provides an incredibly detailed description
of this job, in response to the concerns that many people
had about damaging their wood trim: "It is really simple and
you don't have to be an engineering genius to be able to do
this. The most scary part is actually to remove the wooden
center fascia, since this holds the vent in its place. It
really sits tight. There are four metal springloaded pins
that are attached to the backside of the fascia and are
pushed into four holes which are in the metal dash plate
behind the nice wooden fascia. When the fascia is replaced,
the four metal pins are pushed into their holes and the
springloaded clips are compressed, not in the direction of
the pushing action but by the sides of the holes, since the
clips are V-shaped. Now when you want to remove the fascia,
you first have to overcome this spring action. Since you
think the fascia is waferthin and will break, you might want
to give up, but that piece of wooden fascia is almost 8mm
thick in places. You have to open the glove compartment and
slide the blade of typically a steel table knife underneath
the fascia. Then you must start wedging it away from the
dash. The right side steel pins are app 5mm away from the
top and bottom of the fascia and app 35mm in from the glove
box side from where you will be wedging. The left side
bottom pin is also app 35mm from side, but the top pin is
app 70mm from the side and in the area where the fascia is
only about 13mm wide. Be careful of breaking the wood there.
I hope that by knowing beforehand how things look at the
back it will make you more comfortable to do the job.
"The new vent has four small plastic flanges with holes
in it, two per side along the two long horizontal sides of
the vent. The flanges are about 10mm x 10mm. They have to be
removed, since the pre-'93 cars do not have holes through
which the vent is fixed in position. This is definitely not
needed, since the vent is held in position by the center
piece of wooden facia, and that really sits tight. So, you
have to remove those flanges (can be broken off carefully
with normal pair of pliers) and then just file the leftover
away.
"The other small job is also due to a small difference on
the new vent, but again, this is small and easy to do. The
new vent has has two small D-shaped bulges on both sides.
This will most probably interfere with the metal plate of
the dash where you have to push in the vent. Just mark the
position of those bulges and file away the notches in the
metal plate (About 5mm wide and 3mm deep and halfround
shape; use small round file).
"I did not notice the problem of the new vent being
deeper than the original, as was noted by Dan Jensen. Thus I
did not have to do that filing to make it less deep. My new
vent pushed in all the way until it settled against the
rectangular sponge seal and there was no interference with
the wooden fascia due to a bit of vent protruding. If you do
find this problem, just file away the required amount from
the rear of the vent.
"The correct Jaguar part no for the new vent is BEC26361.
Do remember to buy the new foam seal as well. You are not
likely to save the old seal, as it will have rotted and
deformed.
"You will have complete control over the direction of air
flow both up and down and to the sides. If you live in an
area with hot weather as I do, it is essential. You won't
believe the difference."
Pre-1987
System
TRAINING MANUAL: Jaguar, back in the days of
British Leyland control, issued a "British Leyland Service
Division Dealer Training" manual, "Aid # S1002" on the
Environmental Control System. Although it's described as
intended for the "Jaguar XJ6, XJ12 Series Two", the same
basic system was used in the pre-1987 XJ-S. This book is
long out of print, but if you happen to find a dealer or
mechanic with one you definitely want to have a copy
made.
HEATER CORE REPLACEMENT: The heater core ("heater
matrix" for you Brits) on the pre-1987 XJ-S has integral
pipes that extend through the firewall, where hoses connect
it to the engine cooling system. To get it out intact
requires disassembling the entire dashboard and A/C
system.
Michael Neal recommends shortcutting the heater core
removal to keep from pulling the dash apart. The instrument
pod must still be removed, and dropping the steering column
down is required. But total disassembly can be avoided by
cutting the pipes and installing the new core using short
pieces of hose with clamps. Neal is an official Jaguar
mechanic and highly recommends this method; there is nothing
wrong with using heater hose for such an application, and
disassembly of the entire system is likely to cause further
problems unless done by an experienced Jag mechanic.
Greg Price sends a detailed checklist: "To those who have
to replace their heater cores and want to cut the pipes
rather than disembowel their entire interior, the procedure
is pretty straightforward with the following caveats:
1. You don't have to take the driver's seat out,
but it might make a more comfortable working environment.
2. The steering column must be removed in order to
make room for the heater core to slide out. The steering
column is held up under the dash by four bolts. These
bolts have spacers, washers, seating rings and a steel
piece that holds the nuts. Before removing the steering
column, take out the tach and speedo, then look inside
with a flashlight to see where all of the little spacers
and miscellaneous bits go. Take notes. As soon as you
start to remove the four bolts, all of those bits bail
out.
3. Take a Polaroid picture of the heater mechanism
area before you start taking things out. If you can't buy
or steal a Polaroid camera, draw a very detailed map of
the area, and pay attention to what goes under or over
what.
4. As you remove the screws and such, tape them to a
sheet of paper in the order that they were removed. It
makes the orderly reassembly that much more orderly.
5. Buy the best hose clamps you can find. Get those
swedish jobs that you can torque down with an impact
wrench.
6. Use silicone to seal the hose to the pipes.
7. Cover everything. Twice. Brass shavings fly
everywhere when you cut the pipes (especially if you use
a pneumatic cutoff tool). Silicone always ends up
everywhere except where you want it.
8. Be mindful of the hazard light switch. It's easily
mangled. I think mine will hold together (I hope).
9. Plastic wire ties are great for holding all of the
excess wiring and plumbing up out of your way.
10. Don't drain your cooling system like the manual
says. Pull off the heater hoses, plug them temporarily,
then blow the remaining water out of your heater core
with compressed air. Keep your face away from the
outlet.
11. Watch out for the fiber optic line going into the
ignition switch cover. Remove the switch cover and tape
it up out of the way with the fiber line before you drop
the steering column.
12. If your cruise control doesn't work, now is a good
time to check the steering column wiring and speed set
switch.
"The entire procedure took me about 3 and a half hours
(including a short dinner break), which beats the hell out
of disassembling the dash and console."
BLOWER FANS -- REMOVAL: Fortunately, the blower
fans are a lot easier to remove than the heater core. The
blower housings are outboard toward either side of the car
and connected to the center core with flexible rubber ducts.
To remove each blower assembly requires removal of the
underscuttle cover, fusebox, a couple wires, one vacuum line
and two bolts.
In the Jaguar repair manual, one step in removing the
blowers is to open the recirculation door and block it open.
The next step listed is to remove the bolts holding the
blower in. Please do not infer from this sequence that the
blower retaining bolts are within the recirculation door;
the door must be blocked open simply because it is linked to
the outdoor air intake, which must be closed to prevent
hanging up while the fan is being removed. The blower
retaining bolts are on the outside of the housing and are
obvious. Both steps are necessary but unrelated.
BLOWER FANS - MAINTENANCE & REPAIR: Take the
blower assembly out (it's easy), then take it apart to get
the blower out (also easy) and remove the impeller from the
motor shaft. Look at the motor and see if there's any
obvious damage, like wires hanging out, burnt windings,
foreign object damage, etc.
The blower motors are not overhaulable. The motor itself
is held together by peening over some tangs, and
reassembling would be difficult. However, it is possible to
repair many problems the motor might encounter.
Since the British engineers saw fit to make these
completely open motors exposed to whatever dust and debris
comes through the ventilation system, it may be helpful to
remove lint and foreign objects from the inner workings of
the motors.
Since the bearings are exposed as well, some fresh
lubrication will be welcome, but don't over-oil the rear
bearing; excess oil may find its way onto the commutator,
gumming up the works. Use a light machine oil, like sewing
machine oil.
If the motor looks OK but is seized, force it -- whattaya
got to lose?
Remove the C-clip from the shaft, and remove the stack of
washers against the front bearing; be sure to keep track of
the washers and the order they are installed in. Turn the
shaft and observe the front bearing, which should remain
motionless within the housing. If the bearing turns with the
shaft, a positive anti-rotation modification is called for.
One method is to drill a hole through the steel housing and
into the bronze bearing and install a tiny self-tapping
screw. Make sure the tip of the screw doesn't contact the
shaft itself, and that the head doesn't interfere with the
C-clip and washers.
Pull the little covers off the brushes and remove them.
If they are too short, replace them; don't bother trying to
find original Jaguar brushes, just find some slightly larger
at a motor or vacuum cleaner shop and file them down to
size.
While the brushes are out, use a VOM to check the
continuity at the segments of the commutator. There should
be some form of continuity between any two segments you
test. If you find a segment that doesn't seem to connect to
anything, you're in trouble. If you can see why (a winding
disconnected or some such) you can decide for yourself if
it's possible to fix. Don't use any solder, it won't take
the heat, connections must be made mechanically or by tack
welding.
If you're like me, you'll grind a small flat on the shaft
for the setscrew in the impeller. I just don't like
setscrews on a plain shaft.
Before reassembly, inspect the condition of the three
rubber mounts. If they are dry and hard or crumbling, renew
or fashion suitable replacements from grommets, hose,
whatever.
If your blower fans are toast, Vicarage carries
replacements at reasonable prices.
BLOWER FANS - REINSTALLATION: The rubber duct may
be a neat feature, but it can be a real pain to reinstall.
To make life easier, attach the duct securely to the blower
assembly before installation. I suggest the use of aluminum
tape.
BLOWER FANS - INDIVIDUAL SPEEDS NOT WORKING: The
four blower speeds are controlled by four relays built into
a single unit that is located adjacent to the left side
footwell; the footwell register and the small padded cover
must be removed to get at it. If one of these four relays
quits, one speed of the blowers no longer works, and the A/C
system just skips over it from the next lower speed to the
next higher speed and back. The result can be a little
disconcerting, since the bigger change is speed is quite
noticeable, and since it may be more change than necessary
the system can end up cycling back and forth between the two
speeds a lot when it would have been happier just staying at
the middle speed. Even worse, if it happens to be the "low"
speed relay that fails, the A/C compressor can be operated
without a fan running which is not good on the equipment and
may cause the compressor to kick in and out on its own
thermostat trying to prevent iceup.
This four-relay assembly appears to be a common failure:
this author has had three of the four relays inside it fail,
and others report similar results.
I took the box apart and fixed it each time. The unit is
tough to get out of the car, but once out it is a simple
matter to bend the plastic edges back and pry open; you
might even try bending the edges back and prying the base
out without removing it from the car, since the base
will carry all the important parts and you'll simply leave
the plastic housing in place. Be careful; the NW wires
connecting to the terminal with the screw (and several of
the components inside, if you don't disconnect this wire
before opening) are hot at all times unless you have
disconnected the battery.
The coils are designed to be on continuously, so they
don't burn up; the problem always seems to be broken
connections. The thin wires from the relay coils break off
of the terminals, and soldering them back on makes it work
as good as new. However, there is a theory that these long
thin wires spanning considerable distances within this
assembly are the cause of the problems; a vibration in the
car, perhaps at a particular speed or engine RPM, may
resonate these wires like guitar strings and break them
off.
So, instead of just reconnecting them, fix the problem.
On each coil, the skinny coil wire comes out of the coil and
is wrapped a couple of times around a plastic lug on the
side of the coil before running off to the terminal. Solder
a larger gauge wire to the terminal and route this larger
wire to the plastic lug on the relay and wrap it around a
couple times, then solder the end of the coil wire and the
new thicker wire together right next to the lug. Hence, the
thick wire spans the distance to the lug, and the thin coil
wire is well supported.
Alternatively, just replace the individual relays that go
bad. Brian Sherwood "Found a portion of the fan control
relay was inop, no fan on "low". Removed four wires from bad
portion of relay block and plugged into a generic 12-volt
relay with spade terminals; fan works fine now. Fan control
relay is located in center console, LH side under heater
unit."
The four relays are located at the four corners of the
unit. The "low" relay, at the bottom right corner as you
look at it, seems to be wired with four wires as Sherwood
described. The other three relays, however, each have two
wires going to them, plus there are two commons going to the
whole set of three. A large NW wire provides 12V power to
all three contacts to power the blowers. A small BU wire
provides a common switched ground for all three coils. The
signal to the relays comes via BY, BG and BW wires, and the
power to the resistor pack and blowers is via larger U, R,
and GS wires.
If the low relay fails, you can replace it with a
standard automotive relay, such as those sold for driving
lights; merely remove the four wires from the box and
connect the B and NY wires to the coil and the NW and Y
wires to the contacts, as Sherwood suggests.
If one of the other three relays fails, you can still
replace it with a standard relay. Connect a wire from the BU
wire to one side of the coil (without disconnecting the BU
wire from the other relays on the board), and simply pull
the BY, BG or BW wire off the terminal on the faulty
component and connect it to the other side of the coil.
Connect a heavy wire from the NW wire to one side of the
contacts (again leaving it connected to the other circuits),
and pull the U, R or GS wire from the terminal on the faulty
component and connect it to the other side of the
contacts.
Either opening the box and correcting the problems or
replacing the relays with individual SP relays would
probably save a lot of money; generic "driving light relays"
will work fine are only a couple bucks each. It's likely to
cause less trouble, too; most of the aftermarket generic
relays are quite reliable. You certainly don't want to buy a
replacement four-relay unit from Jaguar -- after all, the
original one is causing trouble, and the replacement isn't
likely to be any better. In fact, it might not be a bad idea
to simply yank the entire block out of the car and replace
it altogether with four generic relays at the first sign of
trouble.
Note that British Leyland Service Division Training
Manual S1002 on the Environmental Control System shows a
separate low speed relay and a box containing three relays;
since the manual is intended for the XJ6 and XJ12 Series
Two, this probably describes an early arrangement. The
wiring schematic appears unchanged, however, and the
replacement of individual speed relays with separate units
will work just as well.
BLOWER FAN RESISTOR PACK: Component #188 on the
schematics. Physically, this unit is mounted in an opening
high on the left side of the A/C system, above the heater
core pipes. Access to the resistor pack is poor, to put it
mildly. If it must be removed, it is suggested that the left
side blower assembly be removed first. It is also suggested
that a small hole be drilled in a piece of structural sheet
metal to allow a Phillips screwdriver to be used on the
upper mounting screw.
For those who need to analyze or repair the resistor
unit, the details are shown in Figure
12. Note that the resistances shown are as measured
on the unit in the author's car, which appeared to be in
excellent condition. The values seem to represent
consistently higher ohmage than in the Jaguar official
wiring diagrams, but the overall scheme is the same.
The speed of the blower fans is controlled simply by
connecting the various resistances in series with the blower
motors. These resistor packs are installed in the airstream
from the blowers so that the airflow will keep the resistors
cool. If the blowers seize or otherwise fail to move air,
the result is often a cooked resistor unit due to lack of
cooling combined with the high current load due to the
mechanical problem.
If one is really cheap or in a hurry, the unit can always
be repaired using Nichrome wire from an old toaster or some
such, or even by twisting severed wires back together. Do
not use solder, as it will melt; all connections must be
mechanically attached. Exact resistance values are
unimportant, since being off a little will only make the
fans run a little faster or slower than original. Note that
this unit is so difficult to get to that it would be nice to
make real sure it doesn't fail again.
BLOWER FAN RESISTOR PACK -- FUN WITH SCHEMATICS:
The A/C system schematics in the owner's manual (my copy,
anyway) and the Haynes repair manual #478 (page 240) show
the blower fan resistor pack (component 188) incorrectly.
They show the GS wire to the fan motors themselves being
connected to one end of the three resistances, as though all
three resistances operate in series. In fact, the GS wire
connects between the 0.85 and 0.425 resistances (as shown in
the illustration above, except the as-measured resistances
are 1.2 and 0.6 respectively). In M1 speed, power is
supplied to both ends of the resistor pack (Y and U wires)
so that the 0.85 resistor operates in parallel with the
0.425-1.275 pair. In M2 speed, power is supplied to the R
wire in addition, so the 0.85 resistor is now operating in
parallel with the 0.425 alone.
The system schematic in the Jaguar repair manual at the
end of section 86 shows the fan resistor pack correctly.
Also of note, the schematic in the Jag manual shows one
additional circuit by which the high speed position of the
control knob will, via diode #D4, operate the M2 relay.
Reason unknown; it almost appears as a backup in case the
high speed relay fails.
DEMIST DUCT VANE: The official Jaguar XJ-S Repair
Operation Manual, Section 82.25.21, step 35 says "Ease
demist duct vane securing studs from screen rail and recover
demist duct assembly." John Nuttall felt this was unclear,
so when he finally figured out what it was talking about he
provided the following explanation. Note this applies to his
1977 XJ-S.
"Removal of this vane uncovers a screw which secures the
unit to the car body just below the windshield. The main
difficulty with the manual is that it does not make clear
just what is the demist duct vane, and I don't think the
official name is a very good description. It turns out that
this object is a piece of vinyl covered rubber about 34 in
(85 cm) long, 3/4 in (2 cm ) thick, and 3in (8 cm) wide in
the centre, tapering at the ends. Along its back face is
screwed (with 13 screws) a plastic air deflector to direct
air to the windshield. This vane fills in the gap between
the centre of the fascia and the windshield.
"To remove the demist duct vane you must undo two screws
placed vertically downwards at the ends. With the windshield
in place it is impossible to do this with a conventional
screwdriver. I was able to turn these screws with vise
grips. The underside of the vane has two prongs about 17 in
(44 cm) apart which engage slots in the unit below."
CONTROLS: Rob Reilly provides the following system
description: "Outside air is drawn in through the grille in
the center of the cowl between the bonnet and the
windshield. Vacuum operated flaps on the fan motors close
off this outside air under certain conditions and draw air
instead from inside the car (known as the recirculating
mode).
"From the fan motors the air goes through rubber branch
hoses to the front chamber of the heater unit. Here
all the air passes through the air conditioning
evaporator and gets cold (if the compressor is on). Then
there are four flaps controlled by mechanical linkages which
can be seen on the right hand side of the unit. These
control what percentage of the air passes through the heater
core and becomes warm (if the water valve is open and the
water is warm) on its way out to the vents.
"The upper front (meaning toward front of car) flap
("upper bypass flap") opens or shuts off cold air to the
dashboard side vents, center vent, and windshield defrost
vents. This air has not passed through the heater
core. Clockwise is open, counterclockwise is closed, viewed
from the right hand side. The center vent and windshield
defrost vents also have vacuum-operated flaps.
"The upper rear flap ("upper heater flap") opens or shuts
off warm air, which has passed through the heater
core, to the same upper vents as the first flap. Clockwise
is closed.
"The lower rear flap ("lower heater flap") controls warm
air to the lower vents on the sides of the transmission hump
and to the duct hoses going to the rear vents under the
center console armrest. Clockwise is open.
"The lower front flap ("lower bypass flap") controls cold
air to the lower vents. Clockwise is closed.
"On the left side is a vacuum actuator and linkage which,
when the selector is on DEFROST, will be up (vacuum off) and
prevents the bottom heater flap from opening.
"There is a servo motor on the lower right which operates
some more micro-switches, vacuum line valves, and mechanical
linkages, and is in turn controlled by the temperature
setting and several temperature sensors through the
amplifier and relay on the lower left.
"The left hand knob (temperature control) turns a
variable resistor. The resistor should have a resistance of
zero ohms at the 85 degree mark and 10,000 ohms at the 65
degree setting. There are three solder pins on this thing,
one of which should not be used. If you had a high
resistance in the circuit the unit would think you're asking
for cold air and would turn the stepping motor to give it to
you.
"The small device mounted on the lower tube of the heater
core is a temperature-controlled on/off switch which
disables the blowers until the water warms up." Actually, it
limits the blowers to low speed.
CONTROLS -- VACUUM LOGIC: The following logic
chart was graciously provided by John G. Napoli:
Jaguar Climate Control Vacuum Logic --
Representative of 1982 XJ-S HE
Compiled by John G. Napoli
|
Control:
|
Vacuum
|
Switch
|
Cam
|
Switch
|
Vacuum Solenoid
|
|
Item
Con-trolled:
|
Screen Flap
|
Lower Heater Flap
|
Water Valve
|
Center Dash Flap
|
Blower Flaps
|
FULL COOL
|
Control Status:
|
On
|
On
|
Open
|
Open
|
Energized
|
|
Item Status:
|
Closed
|
Open, and over-ridden by
flap
|
Closed
|
Open
|
Closed
|
|
Vacuum Status:
|
Vacuum
|
Vacuum
|
Vacuum
|
Vacuum
|
Vacuum
|
FULL HEAT
|
Control Status:
|
On
|
On
|
Closed
|
Closed
|
De-energized
|
|
Item Status:
|
Closed
|
Open
|
Open
|
Closed
|
Open
|
|
Vacuum Status:
|
Vacuum
|
Vacuum
|
No Vacuum
|
No Vacuum
|
No Vacuum
|
FULL
DE-FROST
|
Control Status:
|
Off
|
Off
|
Closed
|
Closed
|
De-energized
|
|
Item Status:
|
Open
|
Closed
|
Open
|
Closed
|
Open
|
|
Vacuum Status:
|
No Vacuum
|
No Vacuum
|
No Vacuum
|
No Vacuum
|
No Vacuum
|
Notes:
- In FULL COOL,
recirculation is enabled because the vacuum solenoid is
energized.
- A NORMAL A/C mode is
therefore implied with the vacuum solenoid
de-energized.
- In FULL COOL, everything
gets vacuum.
- In FULL DEFROST, nothing
gets vacuum (default system operation if system
fails).
- In FULL HEAT, only the
items fed by the vacuum switch get vacuum.
- The vacuum switch is
attached to the right hand climate control knob
(Positions: Low, Auto, High, Defrost).
- The cam switches are
part of the servo. The servo is mounted on the right of
the climate control unit under the dash (next to the
right hand occupant's left shinbone).
- The vacuum solenoid is
mounted on the left of the climate control unit under the
dash (next to the left hand occupant's right
shinbone).
- Water valve is located
on center of firewall in engine compartment.
- Dashboard may have to be
removed to access flaps. Always check operation of and
adjustment of servo linkages when troubleshooting this
system. There are two blowers (left and right). Check
them both!
- Some later XJ-S's may
have a manual override enabled by pulling the right hand
climate control knob out and turning. Reference to this
feature was seen in a 1983 XJ-S Owner's
Manual.
CONTROL MICROSWITCHES: The right side control knob
has microswitches behind it that are often found to be the
source of trouble. However, Ron Whiston points out that the
problem is often not a failure of the microswitches
themselves, but simply that they are incorrectly positioned
relative to the cam; turning the knob doesn't move the
switch enough to make it click. Even though the mount holes
are not slotted and are not intended to provide any position
adjustment, merely loosening all the mount screws and
holding the switches inward while tightening them back down
will often correct all problems.
TEMPERATURE CONTROLLER: Reportedly, the wirewound
pot has problems.
CONTROL LINKAGE ADJUSTMENT:
The Jaguar repair manual describes an adjustment procedure
that is unclear and covers only a couple of the adjustments
needed. The illustrations are tiny and poorly labeled. Below
is a procedure that should enable a more complete adjustment
of the linkage. See
Figure
13 and Figure
14.
While performing these adjustments, keep this concept in
mind: The difference between a flap being fully open and 90%
open is insignificant; there is a lot of airflow in either
case, and the passenger will not be able to detect a
difference. On the other hand, the difference between a flap
that is fully closed and one that is slightly open is huge.
Therefore, the objective of the adjustment procedure is to
make sure that all flaps close fully, and how far they open
will be of little concern.
1. Remove the glove compartment, the
"underscuttle casing" (panel above the footwell) on the
right side, and the grille and padded panel on the right
side of the transmission tunnel.
2. Remove the short steel duct that serves the
footwell grille. Be careful not to drop any screws into
the works.
3. Loosen the locking screw on the lower bypass flap
adjustable link. Loosen the locking screw on the upper
heater flap adjustable link if there is one; if the car
has a facia temperature control (a slider under the
stereo), it will not have an upper heater flap adjustable
link as the facia control takes its place. Loosen the
locking screws on both pullrods where they connect to the
servo control levers.
4. Move the servo to the full cool position, which is
where the levers on the servo are held at their most
downward position. Note that the pullrods are normally
held upward by the linkage springs; with the linkages
disconnected, the servo levers will fall down regardless
of servo motor operation. You must pull upward on them
with your fingers to determine what position the servo is
actually in. Note also that operation of the servo
doesn't move the levers continuously from one extreme to
the other, but rather goes back and forth somewhat; be
sure the motor has moved all the way to the extreme
position that holds the levers in the downward position
before proceeding.
To move the servo, disconnect the main electrical
connector to the servo unit, which is a 13-wire connector
in the same general area you're already working in.
Connect 12V power across the solid purple and solid red
wires; if the battery is connected, 12V power is
available at the nearby fusebox, at fuses 2 or 3 (RHD
cars) or fuses 13, 14, 15, or 16 (LHD cars) so it's a
simple matter to run a jumper from the fusebox -- or
simply from the cigar lighter, and connect the other wire
to ground. If the battery is disconnected, a 9V battery
will also work well, running the servo a little slow but
it gets there. To run the opposite direction, reverse the
power.
5. Turn the main bellcrank clockwise until the lower
heater flap is held firmly shut; it may be easier if the
main tension spring is disconnected. Hold the main servo
control lever up. Tighten the locking screw on the servo
lever.
6. If the car has no facia control, hold the upper
heater flap in the fully closed position (clockwise) and
tighten the locking screw on the adjustable link.
If the car has the facia control, move the slider to
the full right position. Loosen the clamp holding the
cable housing, and move the cable housing until the upper
heater flap link forms a straight line. Lock the cable
housing into this position.
To check the operation of the facia control, move the
slider to the left. The upper heater flap should fully
close, and further movement should be taken up by the
spring in the linkage.
7. Move the servo to the full heat position (levers in
their highest position).
8. Turn the lower bypass flap to the fully closed
position (clockwise). While holding this position, slide
the adjustable link to its longest possible length and
tighten the locking screw.
The lower bypass adjustable link has a slotted opening
to allow the flap to be farther closed than the linkage
calls for. To check that this slider works properly, move
the servo off the full heat position. Turn the lower
bypass flap towards closed, against the force of its
spring. The lever should move smoothly in the slotted
hole. If it doesn't move smoothly the linkage is probably
misaligned, causing it to jam. Determine which way the
parts are misaligned. Take the lower bypass adjustable
link apart by removing the locking screw entirely and
removing the screw holding the lever to the flap. Once
out of the car, carefully bend the parts to correct the
misalignment. Reinstall, readjust, and check for proper
motion again.
9. With the servo in full heat position, allow the
spring to turn the upper bellcrank clockwise until the
upper bypass flap is closed. Hold the upper servo lever
up and tighten the locking screw.
10. Reassemble and test drive.
Note that on later cars there is a vacuum actuator on the
left side that holds the lower heater flap closed when the
defrost is called for. Vacuum permits lower heater flap
operation, lack of vacuum prevents it. To observe the
operation of this actuator, it will be necessary to remove
the underscuttle casing on the left side. There is no real
adjustment necessary, however, since it is either on or off.
Make sure there are no wires or anything obstructing its
motion.
Note that the connection of the pullrods to the
bellcranks is a nut-bushing that is fitted into a slotted
hole on the bellcrank. The procedure above does not address
location of the nut-bushing within the slotted hole. This
position determines the sensitivity of the system; if the
motion of the servo causes the flaps to move too much, the
nut-bushing should be relocated farther away from the pivot
so that the same amount of pullrod motion won't turn the
bellcrank so much, and vice versa if the servo doesn't move
the flaps enough. It is recommended that these nut-bushings
not be tampered with. If their position is altered, the
entire linkage adjustment procedure above should be
repeated.
CONTROLS - RANGE PROBLEMS: Olov Carlsson sends
this comment: "I had a problem with the temperature control
knob being out of range. Even when I put it in the coldest
position, the system wouldn't cool properly. It did work,
however, which I determined by using the cigarette lighter
and holding it under the interior temperature sensor. This
sits in a hole that can be felt under the dashboard centre
shelf. When doing this the system adjusted itself and
cranked out wonderfully cool air.
"There is an adjustment for this on the amplifier unit. I
turned it to the cold end position, but this wasn't
sufficient to bring the temperature control knob properly on
scale.
"My final solution to this was to connect a 10 kohm
resistor in parallel with the external temperature sensor,
which is mounted inside the right side external air intake.
Careful analysis of the circuit diagram and the wiring
allowed me to put the resistor alongside the internal
temperature sensor. I connected a wire to the appropriate
lead on the amplifier unit, the result being that the new
resistor effectively was in parallel with the external
temperature sensor. This one, by the way, did measure the
correct resistance (the same as the internal sensor, when
they both had the same temperature). This brought the
adjustment on the amplifier unit into range making it
possible to calibrate the temperature control knob."
TOO MUCH COOLING: Mike Morrin says, "If the system
works properly for a while (10 minutes) and then drifts
slowly towards full cooling, then the fault is likely to be
in the plumbing to the in-car air temperature sensor. This
is a reference to a couple of cases I have heard of where
the rubber connector inside the dash had come adrift so that
the air temperature inside the dash was being
measured. There is no cold air supply inside the dash, just
heat soak from the engine and heater unit, causing the
measured temperature to creep higher and higher, and the A/C
to pump full cold into the car."
TOO MUCH HEATING: Tom Bernett says, "Note that the
function switch removes the supply from the temperature
control circuit when in the DEF position, and this causes
the system to move to full heating, so a faulty function
switch can cause the system to stay on full heating. But, I
was getting considerable air flow from the side and center
vents when it was in full heat mode."
Mike Morrin explains: "Yes, because the function switch
also has a vacuum valve which directly controls the demist
flaps, and is independent of the electric circuit."
SERVO REPAIR: Mike Morrin says, "After cruising
for an hour at about 70 mph. with the A/C on (of course),
the system all of a sudden went to full heat. I fooled
around with the temp selector and after several minutes it
went back to normal operation.
"It turned out to be a faulty feedback potentiometer in
the servo, so that the amplifier thought the system was on
full cold, so was sending the system to full warm. To check
this you need to leave a voltmeter connected to the feedback
circuit (as per instructions) and see if the voltage goes
the right way or the wrong way when the fault occurs.
"The actual fault on mine was that the feedback
potentiometer is a wirewound type, and the wiper arm had
worn through the wire right at the end of its travel. I did
a quick fix by painting some silver loaded paint onto the
end of the winding, and it has survived for 3 months so far,
I expect another 10 years out of it."
RELAY CHATTER: Mike Morrin, who owns a 1975 XJ-S,
reports on "a tendency for the amplifier relays to chatter
after moving the servo. An oscilloscope across the supply
lines showed noticable spikes when the amplifier relays
operated. I have managed to significantly improve this by
fitting a 1000 uF 50V capacitor across the 12V supply close
to the amplifier. The amount of relay chatter is reduced by
about 80%. I can confirm that driving the car today, the
operation of the servo system was smoother than
previously."
CONTROL AMPLIFIER REPLACEMENT: Aftermarket A/C
control system amplifiers are available for those who either
don't wanna pay Jaguar prices or don't expect that a new one
of the same type will last any longer than the original did.
See H. D. Rogers & Sons.
CONTROL AMPLIFIER REPLACEMENT -- CHEAP VERSION:
Mike Morrin suggests, "...a double pole switch (like a
window lifter switch) can be arranged to drive the servo
manually." Simply connect 12V power through the switch to
the red and purple wires on the servo connector; the two
positions of the switch should provide power in opposite
polarities. Label the button "cooler" and "warmer" or some
such.
1987-On
System (Delanair MkIII)
PARTS: Parts for the MkIII system are notoriously
expensive. Per Hal Rogers, "the Delanair heater unit is
made/supplied by Delanair of England. Many aftermarket
companies have attempted to obtain parts directly from
Delanair but they cannot sell directly because of
contractual obligations to Jaguar."
PARTS CONFUSION: According to Technical Service
Bulletin #8228, there is some confusion as to which A/C ECU
goes with which water temp switch and in which car.
According to their guide, the trick is to check the wires at
the water temp switch on the left side of the evaporator
case. If the wires to this switch are slate and black, the
correct ECU is CAC 8032, the correct water temperature
switch is JLM 763 (red), and the harness part number is JLM
1170. If the wires are green and black, the correct ECU is
DAC 7601, the correct water temperature switch is JLM 2121
(black), and the harness is either JLM 10393 (all
convertibles and 1992-on coupes) or JLM 10394 (1991-92
coupes). We all clear on that? Good.
VACUUM SCHEMATIC: Finding a vacuum schematic seems
to be difficult, so I have included two here -- courtesy of
Victor Naumann. Schematic
1, Schematic
2.
BLOWER FANS: According to Randy Wilson: "Jaguar
doesn't sell the blower separately. They sell the complete
blower unit: housing, motor, fan, and electronics! Yes,
there are electronics buried inside that blower case. Plus,
just to add a bit more, the right hand box carries the
ambient temp sensor. There are also two relays inside the
box." The blower assembly is reportedly incredibly
expensive.
BLOWER SPEED CONTROL REPAIR: Stefan Knappe saved
himself a lot of money: "I noticed that the right fan (it's
got two, left and right) did not work except when the fan
speed was set to max. I took the blower motor out, which is
rather easy on the right side of a LHD car, finding a little
solid state circuit located in the intake part of the fan.
This circuit gets information from the A/C computer and
regulates the fan speed unless the setting is to max, which
actuates a little relay situated in the blower case too. I
found out that the power transistor on this little circuit
was blown. I went to the Jag service asking whether this is
available seperately. But, you might have guessed it, the
blower is only available as a complete assembly, being very
expensive. So I went to an electronic store and bought a
transistor equivalent to the type built into the fan-circuit
(Texas Instruments #2N6284). I soldered it in, put the stuff
together and the fan worked from that time on without
problem."
Martin Sellars adds, "Air con blowers: these devices
contain an electronic circuit which gives speed control for
all settings but "high". This comprises a Darlington
transistor 2N6284, a 68 Ohm 2.5Watt resistor, a 1N5401 diode
and a small glass diode, probably 1N4148 or 1N914. All these
parts are easily obtained cheaply from electronic component
outlets (example; in the UK Farnell Electronic Components,
+113 2636311, but ask for a catalogue to get the right order
numbers). Blowers that won't run at low speeds almost always
have a failed transistor, but replacing that alone won't
always fix the fault. The resistor is there to protect the
transistor from voltage spikes produced by the motor, so
check the value and replace if it isn't right (most hobby
multimeters have an Ohms measurement feature). The small
diode feeds the blower motor voltage back to the AC
computer, and has steel leads which corrode away, breaking
the connection and preventing speed control from working. I
replaced mine with 1N4004 types, which are much more rugged,
more easily handled, and cost just a few pennies more. These
diodes are fitted with their cathodes (marked by a bar on
the body) towards the transistor collector (the steel case).
The 1N5401 diodes are very rugged, and unlikely to need
replacing. When fitting new diodes or resistors, don't try
to fit them inside the blower interior, like the originals,
where they are prone to corrosion. Fit them on the solder
side of the PCB (having snipped out the old parts) and then
cover them with the original plastic flap using some
tape.
"I also fitted new brushes to the blower motors, using
power drill spares filed down to the right size (Kirby's
tip!).
"Inside the blower assembly is the high speed relay,
which is also prone to dirt and corrosion. Standard car
accessory shop units can be used here, but check the pinout
- I think they are not standard, I had to rewire mine.
Considering the cost of a new unit, changing the parts
mentioned above gives "as new" performance at a tiny
fraction of the cost."
COMPUTER PROBLEMS WITH BLOWER CONTROL: Stefan
Knappe cheated on this one: "Another problem I had on a
friend's car, on which one fan did not work. After checking
the fan, I found that the A/C computer (located on the right
hand side of the centre console, take cover underneath glove
box out) delivered signal to one fan blower only, the other
signal line being dead. Computer gone (at least in this
respect). I asked for the price of a new one and decided
immediately to go for another solution. Since I'm not so
deep into electronics to repair this difficult thing itself,
I had another idea. I cut the signal line which was dead and
connected it (the line to the blower) with the good one for
the other side. Both fans worked again. Risk was that the
computer will be damaged on the good side due to higher
current delivering two circuitries, but on the other hand
the thing was already gone... This solution proved to be
okay, since it still works and the repair has been done
three years ago.
"Caution: Don't check power output anywhere in the system
with a lamp or bulb, use a voltmeter 10 MOhm impedance,
otherwise you may damage the computer!!"
TEMPERATURE SENSORS: Martin Sellars says,
"Temperature Sensors: the Delanaire system uses three, all
are electrically identical. They measure ambient air
temperature (mounted on the RH blower housing), in car
temperature (above the glove box, behind a small aperture in
the dash) and on the evaporator. These have three wires to
them, power (5Volts from the ACC), ground, and the output
wire. The output voltage is very closely controlled at
2.785V at 0イ and rising by 0.01V per degree C. So, a sensor
at 20イ (about 68ェ) should read 2.985V, and at 30イ (about
90ェ) should read 3.085V, and so on. I found these can be
measured reasonably easily with a standard 20k/Volt moving
needle "hobby" type multimeter, at least well enought for
fault finding purposes."
Richard Mansell quotes from a Jaguar publication on the
changes for the 1992 model year:
The
air-conditioning in car sensor now uses the motorised
aspirator/sensor from the XJ6 allowing a more accurate
reading of the true temperature of the cabin which will
be less susceptible to drift or overshoot.
DUMB PROBLEMS: Martin Sellars: "My car showed very
erratic operation of the A/C, sometimes OK, sometimes wrong
settings (hot on hot days and vice versa!), sometimes no
action at all. This fault might have been blamed on the
computer - but in fact it was due to moisture coming out of
the evaporator, and running down the RHS of the transmission
tunnel onto the single in-line fuse holder that carries the
supply current to the A/C computer. The contacts had
corroded slightly, breaking the supply current, and giving
intermittent operation of the A/C. A new inline fuse, plus
fixing the drainage, solved the problem."
WHILE YOU HAVE THE BLOWERS OUT: Martin Sellars:
"While the blowers are out, access to the evaporator is much
easier. The four short tubes which couple the evaporator
body to the rubber blower ducts can be twisted slightly and
removed. This allows slight access to extract some of the
gunge and detritus that blocks up the drainage system,
causing wet carpets, rusty floors, and other problems."
HEATER CORE REPLACEMENT: Those who must replace
the heater core should thank their lucky stars if they have
the Delanair MkIII system. A major design feature of this
system is the ease of replacing this core, a major task on
the earlier cars. The Delanair MkIII system has bolt-on
pipes for the heater core, eliminating the need for the
"shortcut" pipe-cutting procedure devised for the earlier
system. Also, Per Michael Neal, "The heater core is
removable from the right side. There is a large piece of
black tape, similar to electrical tape, that covers the
access panel. Removal of the core is simple as unbolting the
pipes, pulling the glovebox and access cover and removing
the core." This eliminates the need for removing the
instrument panel and dropping the steering column, as on
earlier models.
HEATER CORE PIPE ATTACHMENT BOLTS: Per Julian
Mullaney, "There was a problem of dissimilar metals causing
corrosion of the bolts which attach the pipes to the brass
core. The pipes and heater core are brass, the screws
holding them together were steel. I guess stainless bolts
would be better. You could replace them as a preventive
measure."
HEATER CORE PIPE ATTACHMENT O-RING SEALS: Per
Julian Mullaney, "The O-ring seal used at the connection
point appears to be of a terrible design. A mechanic once
told me that these O-rings always go first."
For anyone who doesn't think the resultant leaks would be
a big deal, Mullaney adds: "This leak really screwed up a
lot of stuff under there. The drips ruined the A/C amp,
connectors, and my CD player."
Apparently Jaguar realized the seriousness of this
problem. According to Michael Neal, "Jaguar has a gasket to
replace the O-rings. It is shaped like the mating pipe of
the heater core and is made out of a silicon/rubber type
material." The part number for the gasket is JLM 759; you
need two to do the job.
According to Mark Roberts, the "condensation
deflector shield" being added to systems by Jaguar is
actually a result of these connections leaking on
radios!
On to the
Electrical
System
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