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Wiring Questions

Wiring Questions

I have a follow up question on wiring to fog lamps on 140 OTS. I think
everyone cocurred that a wire ( or Harness) ran from the switch to the
front of the car where it splits to go to each light without any plugs or
connectors. The wire should be braided red/yellow, my question is should
the single red/ yellow wire have a black braid on it as well as is typical
when more than one wires run together ( a harness)

My second question. There is a white tail in the engine bay harness a short
distance from the fuse block which I assume goes to the coil. How does
white (#9) then get to the thermal unit and the electric choke. Should it
run back through the engine bay harness, or is this a seperate wire ( or
harness) I do not appeared to have been supplied with either option. The
wiring diagram is not clear as to weather it goes to from coil to choke
first or from coil to thermal switch first. Thanks in advance.
Neville Laing

Well, I haven't got an XK140 but the Mk V has the same ASC on the carb. The
feed for this is from the fed side of the coil to the ASC body, then the
other side of the ASC goes to the Thermo switch and that's it. When the
engine is cold the thermo switch makes the circuit, the ASC is fed with 12v
and the flap valve thingy inside opens to enrich the mixture. As the engine
warms up, the thermo switch goes open circuit and the juice stops flowing
in the ASC and the flap thing closes.

I personally don't like it as it is too crude in operation and I find that
the car runs so rich when the carbs are set up OK when cold that it doesn't
cut out early enough so I have taken the wire off the thermo switch to a
manual cut out switch so I can shut it off earlier than it would have done.

Dick Clements
1951 3.5L Mark V Saloon (passion)
1977 Ford Granada 3.0L Saloon (dormant passion, but probably up for sale)

re: white tail -- on my 140dhc a "tail" (believed to have once been white)
emerges from the main harness along the "off" side of the engine bay near
the aft clamp on the upper rad. hose...goes directly to one of two spades
on the neg. coil terminal (I can't swear that the coil is in correctly, but
the routing is the point) a short wire goes from the other spade on the
neg. coil terminal to the electric choke. a second wire from the choke goes
to the thermal switch, to be grounded when cold.

Re: fog lamps...the wires to my fog lamps appear to originate left and
right from small (4 terminal) connector blocks on the left and right
inboard face of the sheet metal ahead of the radiator, near a round
horizontal cross brace. The wires to the fog lamps and, I think, the horns,
come off the top of the small blocks, pass immediately through grommets to
the under fender area and down. The supply wires to these blocks are fed
through another grommet just below the blocks from the under fender area.
The whole point appears to have been to have those connection blocks
readily available in the area ahead of the radiator by simply opening the

N.B.: Major Caveat (sir) A very knowledgable person (who shall remain
nameless, but whose initials are Wray Schelin) opined, from photos only,
that my XK 140 had XK 120 front this description may have no
bearing on your situation...John E, Roger P. helpppp!

Could Jaguar have had 120 fenders about when the 518th Drophead was built?
Jim Warren '55 XK 140 DHC 817518

If you believe the wires on your car from the coil to the choke and from
the choke to the thermal switch are correct could you describe them. Are
they white braided insulation or do they have black rubber like cover
possibly giving better protection against heat. Are they supported in any
way to prevent contact with hot surfaces.
 Neville Laing

(1)- harness to coil: appeared white, no support, had a plastic outer
sleeve over braid most of its length (can't swear it's orig.) (2)- coil to
choke: unsupported, appeared dark in color but may be due to environmental
factors (it's been oil soaked for years!) (3)- choke to thermal switch:
unsupported, could have once been white (again, "environmental factors")

Jim Warren

The wiring diagram needs interpretation to be understood. The white (9)
wire goes from coil (SW) to starting carburettor solenoid terminal. From
the the terminal on the other side of the solenoid, wire goes to the
screwpost on top of the thermastatic switch, which is direct earthed to
inlet manifold when switch is closed (cold) thus energising solenoid,
activating starting carburettor. The Earth symbol off the thermo-switch
incorrectly suggests an earthing wire.
NOTE: NO spade connectors on an XK140, all connections should be 'Bullet
Connectors' or 'Screw Connectors' or 'Ring-type' or other special
connectors, so if your cars now have spade connectors on Coil, or
Thermo-switch or other components, you've got more modern replacements.

Roger Payne

Spade, schmade 140 hasn't been on the road for twenty years and needs
at least five years of restoration ;~p
Jim Warren

Neville, I will give you my thoughts though I am completing a 150 FHC.

I would think that the basic harnesses between these models would not be to
far off. At any rate, here goes. I'm composing this at the office and don't
have a car or diagram to talk from, only my feeble memory.

If I am understanding you right, it appears as though the fog light wiring
(red and yellow wires) is not showing in the dash (cowl) harness. In the
150, these wires are in the dash (cowl) harness going to the light switch
unit and, at the other end, going to the fuse box terminal area. I can see
this arrangement clearly. I'm getting a little fuzzy from this point but it
seems like the engine/headlight harness then starts the fog light circuit
at the fuse box terminal area and goes to the 10 and 5 block connectors
near the grille on the 150. From there, a short, separate harness would go
from the block connectors to each fog light. I may be wrong on this last
part of the circuit since I haven't completed the installation of the fog
lights at this point. As an alternative, It could be that the lights are
fed with individual wires from each block connector, i.e., the 5 block
connnector feeds directly to one light and the 10 block connector feeds to
the other light.

Wish I could help more. Good luck.

Bob Oates

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