I am trying to rebuild the damaged brittle harness on my 1989 XJS Coupe with Lucas distributor. There is a small harness that plugs in on the passenger side firewall. The molded plug has seven wires coming from it going to the coil (white), oil sending switch(black/brown), another sending switch with a rubber boot on it(white/brown), micro switch on throttle(green) air switch under air cleaner pass side (green) to A/C compressor plug(green/brown).
My problem is a green/white wire that goes to the other side of the throttle micro switch making this wire 8. I have no idea where in the harness this wire is supposed to be attached. Are two of the wires from the micro switch tied to one of the green wires? After I removed all of the tape covering the harness it was in the bundle and several were broken.
Any body out there able to help me with this? I have the wiring diagram, but am not very good at reading them and I'm not sure if it goes to that level of detail.

 

Unlike Uk spec cars which do not have it, are you referring to the microswitch on the actual capstan?

Or, like UK and USA spec cars which both have it, are you referring to the microswitch on the engine end of the throttle cable, the last thing on the cable before the capstan?

Greg

 

Yes. The one on the end of the throttle cable

 

This is the kickdown switch. When your foot is hard down, there is a little bump on the cable that triggers the switch. Get a friend to do this (with the car not started !) and you can see the action of the mechanism. Sometimes it jams, but lots of WD40 and lots of accelerator pedal pushing will see it free off with any luck.

There should be 2 wires to the switch, same colour. One is live (ignition on) and the other goes back down over the bell housing to a terminal on the gearbox LHS. When the switch makes the circuit, current goes to the gearbox terminal and trips a solenoid inside that activates the kickdown. As long as you can find the wire to the switch carrying current, you can always (with difficulty) run another from the switch to the gearbox terminal. If you need a gerabox photo, post again. The kickdown terminal on the G B is a male push on connector rear of the selector lever cable end.

Greg

 

Greg, Thanks for the info. It looks like the previous owner didn't know where the wire went so he tucked it into the harness. Does it matter which side gets attached to the micro switch? Does the one from the tranny go to a particular side of the switch?

 

No, it does not matter as long as both wires are connected to the microswitch. Once the switch closes the current earths via the solenoid.

Greg

 

Thanks for your help Greg. A big help!!!