My dash lights are not working on my '92 XJS. I have power at the #18 fuse, next place I checked was the dash rheostat and have no power at that connector. Am I right to assume that the first place the wire goes after leaving fuse block is the rheostat?

 

Andy,

Apparently the fuse output goes to the dimmer control unit and the rheostat switch is fed from that.

Paul

 

Thank you! I thought that relay was only for the overhead and door lights.

 

So, with working interior door and overhead lights, I don’t have any lights to cluster or dash.

on the lighting relay/module, with headlight switch on, I have 12v at the red/blue wire at center of relay and nothing at red/white from wire below it (which I’m pretty sure is the dash light wire but correct me if not).

so, I’m guessing this relay is toast? Or I read something about some wires being splice/connected in this bundle, is it these?

another question, can I bypass the relay for just the dash lights? Run a jumper from blue/red to to the red/white wire?

 

Andy,

There are three wires connected from the control unit to the rheostat switch. They are Red, Orange and Pink. I don't know which is input or return of those?

The Red & White wire from the control unit is the feed to the various light areas including the instrument pack, gear selector, door switches etc.

Good luck

Paul

 

Thanks for response! According to the wiring diagram the red, orange and pink are all "inputs" from the rheostat. I'd like to know how to bypass that on a facelift car (since it has 3 wires, doesnt see intuitive)

Also, I guess I don't understand what this dimmer control module is doing. its got several inputs from ignition switch, the headlight switch and the side light relay in the engine bay (and rheostat) and the only thing it's controlling is the dash and radio lighting.

I took the dimmer module/relay apart and didnt see anything noteworthy. I can't test with another relay since its unique (waiting on a used replacement).

It seems like I could bypass the entire dimmer module entirely by running the red/blue wire that is activated by headlight switch directly to dash light wiring--any thoughts from the experts? I know they put the dimmer module in there for a reason but maybe its like the rheostat and ultimately not needed?

 

Andy,

The module controls the flow of current to the instrument, centre console and door switches plus the radio, so that it only flows with the ignition on and sidelights on. The rheostat takes a current feed from the module and then feeds it back based on the rotary position of the rheostat. So I read the wiring diagram as the current feed back from the rheostat to the module is on the Orange wire (I think!)

If you disconnect the 3 wires from the rheostat and connect them all together, you'll get maximum flow back to the module and hence out to the illumination circuits.

Cheers

Paul

 

Well, I think this subsystem qualifies as one that makes you say, “Why Jaguar?”

I replaced my lighting “module” (which is really just a relay) with a used one and have dash lights again. After studying the wiring diagram and listening to the experts here, I am still unclear why Jaguar couldn’t just run a 12v wire from the headlight switch to dash, console and door lights. Take a look at the interior of lighting module /relay for effect—it’s complicated.









but takeaway for future searchers is that if this relay fails, all other lights will work except dash/console/door lights.

on the pics, I’ve circled in red the space where the trip computer would be on my 92. I can’t find one and so the lights for it are shining through the black felt tape I used to camouflage its absence.

also, I thought I’d repaired my speedo faceplate perfectly when it cracked, but my fully functioning lights prove me wrong. Ugh.