OK, I've searched the forum and read a lot of threads. But nothing seems to mirror my problem with the left rear brake bulb on my 2000 XKR.


I see no evidence of overheating of the ground, nor corrosion. I added a temp extra ground to check that possibility anyway, but no dice. All other bulbs in the tail light unit function properly. I am not getting a bulb failure error message.


Multiply swaps of bulbs eliminate the bulb as a problem. Left brake bulb functions normally, as does the deck mounted third brake light unit.


Here's the really confusing part...I have good voltage at the left brake bulb socket with brake pedal depressed and the bulb removed, but with the bulb in place all voltage to the socket is lost.


Any ideas?

 

I would say you have a wire that is breaking down under load. Run a temporary power line to the lamp and see what happens.

 

The 'bulb socket plate' of the brake light assembly is essentially 'one large, single piece, metallic, carved circuit board'; see attached pictures, or pdf, if it uploaded. If you look at the 'board' you can pretty much figure out where the connection is breaking due to fatigue under stress, probably where the 'bulb spring tab' thing meets the 'ground board?'.

Also credit to whomever took these pictures and this Tail Light Fix Procedure.

 

I'll try that.



I can find no evidence of breakage, but I shall search again.


Thank you both.

 

I ran power from the functioning brake light (right side) to any and all points of contact for positive, and with no extra ground in place, that makes the left side bulb function every time.


I added a strongly attached supplementary ground to the left side, and it made no difference...with the power feed through the harness plug, no brake light.


I added a spot of solder to ensure a good connection between the board and the bulb base spring tab, though I could neither see nor test any lack of contact there. No difference, no brake light.


Still, if there is a bulb in the left side brake light socket, all power is lost; at the bulb, at any point on the board, AND at the harness plug. Without a bulb in the socket, power is present all over the board and at the harness plug prongs.


This is the same with four different bulbs, all of which work fine in the left side unit, and also if power is patched from the right side unit to the left side.


Bumfuzzled, am I.


Any other suggestions?

 

The problem is almost definitely the wiring to the non working side. I don't have my diagrams handy and I can't remember if there is a module.

Trace the brake wire back to where it comes from and replace it with the temporary feed. If your lights come on then, you have a break in the original line that has to be replaced.

 

Elaborate please..."back to where it comes from"?


You're kidding, right ?. That would require tearing the interior all out, I suspect.


You must mean by use of a wiring diagram, no?

 

For the sake of only a few £ ($) might be worth just swapping in a replacement Jaguar XK8 XKR 1996-2001 LEFT REAR LIGHT BULB HOLDER **FREE P+P* TAIL LAMP | eBay

 

It might I suppose, but there is zero indication of fault with the bulb holder, as I see things. Maybe I'm mistaken, and if someone can make that case for me, I'm all ears.


It's not a very complicated item, pretty easy to see all the works and test for continuity.

 

I will dig out my drawings tomorrow but suffice it to say, you have proved it works with a power lead from the other side. Therefore the problem is in the existing power lead to the non working side.
That wire is breaking down under the load of the lamp.

In order to keep you legal, for the time being run the temporary feed from the other side, as you did before to get the light to work and I'll get back to you with exactly where you need to look next.

Sorry but it's late over here.

 

I appreciate that, Jim...very much. I had about come to the same conclusion...your suggested temp fix will keep me legal for the time being.

 

Good point. I guess the left and right holders are interchangeable from the connector point of view so could easily exclude the bulb holder by swapping in the other one before laying out for a perhaps unnecessary part.

 

Looks like it comes from the lamp control module which is in the boot/trunk.
So it shouldn't be too hard to ring out the wires.
It looks like some of the lamp labeling is wrong, but you can figure it out.

 

With those symptoms, the module itself is definitely a suspect.

If you dont' find anything conclusive with the wiring, pull it from the trunk fuse box and open it up. Look for signs of overheated components.

It's easy to remove and once it's out, the covers just unclip.


P.S. Also check Fuse #21 (5A) in the trunk fuse box if you haven't already.

HTH,
Mike

 

I don't think the connectors are interchangeable...mirror images of each other, as I recall them now.

 

For the time being, I am up and operational, a temp jumper line from the working right side to the non-functional left side has me with both brake lights doing their thing. Thanks, all.




Anyone have a picture of the lamp control module? Not at all sure what I'm looking for there, though once located I expect I can worry my way through the rest of the problem.


Not checked that fuse, but will tomorrow first thing.


P.S. Y'all are the best...thanks for the help so very much.

 

Ok, the lamp control module is located aft of the battery and has 1 yellow connector going into it.
From the stop lamp relay the circuit splits via 2 fuses. F6 5A is for the stop lights, F21 5A as stated above is for the tail lights.

Disconnect the yellow plug in the lamp control module and the plug at the left hand light cluster. Now continuity check the blue wire which is the power feed for the LH brake light. You should be looking at a reading of around 0.1 - 0.2 ohms, anything significantly higher than that then the blue wire is at fault.

If the blue wire checks out ok then the problem could be the resistor in the module. Let's see what we get with the above checks first.

 

Thanks, Jimbo.
Sorry - it was late & I gave duff info. I wouldn't expect fuse to be blown, just make sure the contacts are clean & it's seated properly.


Mike

 

Y'all are the best, and I can't thank you enough, not only for the help with this issue, but with many other little items I've been working at to bring this beauty up to snuff over the last year and some.


Now here's the resolved fix...found this this afternoon in the midst of a wash and under hood check and mild detail.


MICE!


I found a severed black wire and a severely chewed green/yellow banded wire. Located nearly underneath the power steering fluid reservoir...how I noticed it is a mystery in itself . There are three exposed wires there, just very short loops outside of plastic conduit/tape.


I did a quickie strip and twist on the black (I figure it must be a ground that affects SOMETHING related to the left brake light fixture), and after pulling my temp power jumper...it works!


So I fought and cussed the tight working space, but got the wires patched with solder and tape. It's not real pretty, I like a cleaner finish for my work, but under the space constraints, it'll have to do .


Here's a picture of the damage, now repaired and working properly.


Wonder what those wires really do .

 

This should be put in the STICKY section; Beware, check wiring for Rodent damage.

I am surprised it did not strike me earlier. I live in the Pacific North West also, and was in charge of dealing with the GSA vehicle contract onsite. The rodent infestation was bad that far out in the Area. They would nest in the engine bays, trunks, and interiors of the vehicles and jump out, or crawl up your leg while driving the car; we had to set traps in the trunks and warn visiting scientists.

One year we had a particularly bad rash of O2 sensor failures on the new Alero's, the wires were being gnawed through at an alarming rate due to the type of insulation that was used as heat shielding on the O2 sensors. The only thing that ended up stopping them from damaging the insulation was to wrap that section of exposed wire harness with aluminum foil and tie wraps, they were completely uninterested in the rest of the vehicle's wiring.

Glad you found the problem.