Another Series III Climate Control Modification
This is a follow-up to my earlier post on a modification to the climate
control system. With this mod. it's possible to have fresh air
ventilation, a functioning temperature control knob and servo unit, and
functioning temperature sensors for system control. The blower fans and
A/C compressor are disabled. It is useful in all but extreme
temperature situations. The system is easily returned to normal
operation for heating or cooling in extreme conditions.
These instructions are based on an '87 XJ6 SIII U.S. federal spec.,left
hand drive, with the Delannaire Mk. II system.
In it's simplest terms the mod. can be described as follows:
1.) Remove the left hand console side casing and the underscuttle
casing. The Water Temperature Switch is located above the black
footwell vent. It's attached to a water pipe and has two connectors
attached to it. One connector has two brown wires, the other has two
brown w/ yellow stripe wires. Undo the connector with the brown/yellow
2.) Remove the right hand console side casing. Find connector P2.
It's located down low and aft. It's a circular white connector, maybe
an inch in diameter with about 10 wires. Cut the brown wire between the
connector and the servo unit. Cut it in the middle so you'll be able
to connect to it later. Careful, don't cut the brown/yellow wire by
mistake. You want the solid brown one.
That's it. Try it out. Turn the ignition on and the mode switch to
Auto. (If you have the Gardner and/or Napoli mods, switch those off)
The servo unit should respond to the temp control knob, the blowers and
compressor should be off, and if your moving, fresh air, conditioned
according to the setting of the temp. control knob, will be flowing
through the dash and footwell vents. Defrost position on the mode
switch should still function.
To return the system to normal operation, reattach the connector at the
Water Temperature Switch, and connect the two ends of the brown wire you
cut at connector P2.
All that remains is to come up with a convenient way of doing the above
switching. It can be done with a simple double-pole, single-throw
toggle switch or a double pole relay. I'm going to use a relay and
control it with the window master switch.
WHY IT WORKS:
The system is designed such that the heating mode is disabled (no
blowers or compressor) until the coolant comes up to temperature. This
prevents a blast of cold air in your face when you first start the car
on a cold morning. After several minutes of running, the coolant warms
up and the system clicks into action. This is controled by the Water
Temperature Switch. This switch closes when the coolant reaches
40°C/103°F and allows the system to operate normally.
Now, just as you don't want a blast of cold air in a cold car, you do
want a blast of air immediately when you start up a car that's been
sitting in the sun on a hot day. This is accomplished by a Water Temp.
By-pass Switch and some fan switches in the servo unit. These are
powered when the system is in cooling mode no matter what the coolant
temperature is. So they override the above Water Temperature Switch.
These switches are powered via the brown wire at connector P2.
So, opening the circuit at the Water Temperature Switch disables the
blowers and compressor in heating mode, and cutting the brown wire at
connector P2 disables the blowers and compressor in cooling mode. In
both modes the temp control knob, in-car and ambient temperature
sensors, servo motor, fresh air flaps, etc. still function.
I envision using this mod as my on/off switch. I'll leave the mode
switch in Auto, and this switch open in all but extreme conditions.
When I need max heat or A/C, I'll close my switch and the system will
operate normally with both blower fans and A/C compressor.
If anybody decides to try this, please let me know what you think. I
just did mine yesterday, and so far it's meeting my expectations
perfectly, but I'd like to know what others think.