Title says it all. Third brake light works fine. Bulbs in the back are fine. No voltage to either brake light bulb when pedal is pushed in.

All other lights at the rear of the car function as they should. Ideas?

Jess

 

Well, since the upper brake light works, the circuit is fundamentally operational.

I suspect a problem with the bulb failure unit for the brake lights, as power for both regular brake light go through the bulb failure unit but power for the upper brake light does not

Cheers
DD

 

Go the the brake light bulb failure unit. Remove and jumper together the three Green/purple wires. Do the brake lights now work?

(Make sure to mark where terminals the wires came from!)

Cheers
DD

 

Where is the bulb failure unit located?

Jess

 

Under the console, on pre facelifts anyway, remove the cubby box lining and you should be able to see it

 

When mine didn't work (no 3rd light) it was the blue relay up in the rear left wheel well. Swopped it out with the new replacement black relay. '91 V12 facelift

 

We went hunting for it today and couldn't find it. This is an '89 coupe if that helps.

Jess

 

UPDATE:

Fixed. The unit had come slightly unplugged, not enough to tell it from looking at it but the connectors weren't doing their jobs.

And it was where you guys said it would be, too. They just didn't see it on first pass.

Jess

 

Searched the forums tonight, because my center/high brake light *works*, but the main brake lights do NOT work. So this looked like a perfect thread to help me fix the problem.

However, I have no idea what I'm looking for. I found the following connector with a bunch of black leads going in, and just two output leads. It is marked "Lucas" something, so probably not aftermarket (there are a LOT of aftermarket wires down in there - a PO had added both a cell phone (one of those big units - great conversation piece) and a CB radio handset (no big box that I can immediately locate...).

So I'm wondering if the attached photo shows the bulb failure unit that you folks are talking about. There are two leads that *look* like they should go in this unit, but they are just hanging out. No idea which of the holes they should go in, though.

Is this the bulb failure unit??


Separately, there is another connector that also mystifies me. It is blue plastic, with three leads. It appears to me that it is combined in the original wiring loom (i.e. not an 'aftermarket'), but I cannot, for the life of me, find anything to plug it into. Does anyone know what this is?


Mystery connector in the console....driver's side, between the shift mechanism and the seat heat/lumbar controls.

 

The bulb failure unit is #8 in this illustration

https://parts.jaguarlandroverclassic.../brand/jaguar/

It should look like this, or close




Don't know what the blue connector is.

The black thingy with the nibs in a circular pattern is the light source for the fiber optic light system. There's a single bulb in there to provide light to the fiber optic cables

Cheers
DD

 

Doug,

Thanks for the very quick reply. So for the fiber optics (no idea what isn't getting light at the moment) would I be correct in assuing I could stick those additional cables into any open/available socket? Are there unused ones, and if so are they blocked off? Should I turn the lights on and just pick two that show some light coming through?

Brad

 

Been a long time since I fussed with the fiber optics, Brad. I think some of the sockets are clear and others have a green filter.

As I recall 6 cables were actually used, to light the ignition switch, headlight switch, and the two each for the two climate control dials

Someone with a better memory will come along

Cheers
DD

 

Yes. Just plug them into any ol empty slot. The light inside of the housing is ONE color (the brighter and whiter the better) any differences needed in lighting color between the source and the endpoint will be handled in the filament or in the unit itself... I would take the opportunity to pull the bulb and replace it. Mine worked when dug out but I was surprised to see the difference a new bulb made. This sounds bad, but I'm not sure, I THINK I used a LED 5 sided light of the correct size to replace the old wire filament bulb. But I could be wrong.

 

For the blueish purple connector. Do you have a working Speedo, cruise control and trip computer? It might just be me and loose association BUT much to do with the connections for the sending unit for the Speedo control/signals on my car are that style plug. I can't say for sure. It's crazy because I had my console out for weeks during the interior rehab. Still, I don't know for sure.

 

How do I get to the bulb?!?

 

Yep, the speedometer, cruise control and trip computer all work (well, the trip computer has been a bit flaky from time to time, especially in cold weather. I often get the "8.8:8.8" display that others have mentioned here in the forum. Per one discussion, while I've been in the console for this repair/sleuthing work I went ahead and disconnected/reconnected the display head of the computer to see if that would give it more stability.

 

So if jumpering the wires brings the main brake lights back online, I assume the conclusion is that the bulb failure unit is bad. Are those available, or is there a component-level "usual suspects" list to attempt to fix it?

Brad

 

From memory, the casing that houses all of it, the bulb, it's socket and the lead outs for the fibers is soft at at least one end. If not that it should just be a 1/4 or a 1/2 turn to open the thing up. Its an interesting design. A mirrored finish inside casting the light into the strands of the fiber optics... Be gentle with it,,, just before ya start yanking on it, lol...

 

My rear lights sensor died and when I opened it (mind you, my hands aren't made well for delicate parts) the 30+yo copper and coils inside of the unit had all but disintegrated. If they hadn't, they might of in trying to fix them. At the same time my car was pretty badly abused so maybe water had gotten into mine and left them in that state.

I would search XJS Parts/salvage on eBay, and write a single generic message and copy and past it to a BUNCH of folks who are parting out a car. I only say that because someone has figured out that it about time for these things to start failing big-time and they can run a premium new... Jus say'n

 

Google "C42291 Jaguar" and see what comes up

And/or contact Dave at:

Everyday XJ

Great guy, great source for used parts

Cheers
DD