So, it looks like I'm suffering the same brake light failure others have faced. I discovered tonight that I have neither 3rd (high mount) nor main RH/LH brake lights, reverse or rear fog lights.

I've searched and read the various threads on brake light problems, and have a good list of things to test in the morning.

But I noticed a few things so far:

1) I've been having intermittent, but increasingly common failures of the shift interlock triggering with the brake depressed. It has now become pretty typical to have to stab the brake a couple/three times to get the solenoid to release the shift lock so I can shift out of park. But it has never completely failed and not unlocked. This is still the case.

2) The 3rd (high) brake light does not light when depressing the brake pedal, however the brake switch is causing the shift interlock to "click" and triggering the shift interlock, and I can shift.

3) The main RH/LH brake lights do not light when depressing the brake pedal, however the brake switch is causing the shift interlock to "click" and triggering the shift interlock, and I can shift.

4) The rear fog lights do not light.

5) The reverse lights do not light.

6) All other lighting, headlights, front fog lights, marker lights, turn indicators and hazards work.


I discovered the problem tonight when I went outside to test a new LED bulb in the 3rd light, which upon installation did not work. That's when I discovered the situation above. So I don't know if my testing of the LED somehow had an effect, although I don't see how, or if my brake lights worked earlier in the day or not. In hindsight I should have tested the brake lights before fitting the LED bulb, but who would have thought to for something so simple. Ah well.

The other thing loosely related is that my battery went dead this weekend because I had the doors open for a while and had the headlights on for a while. I charged the battery overnight, and the car starts fine. But I'll put a meter on the battery in the morning to see what voltage it has. However, to be clear, all the test above was done with the engine running.


One thing I wonder is what circuits run through the brake light switch. When I look at the technical drawings I see a connector with four wires.

http://www.wellsve.com/custom_search...ngs/SW9225.pdf

So that makes me wonder if the switch has two circuits, one for the shift interlock, and one for the brake lights. If it does have two circuits in that configuration, it is possible that even if the shift interlock is working in the switch, the brake trigger circuit may not be. So the "click" test may not properly identify a broken switch. Do we know where the brake trigger circuit from the switch terminates so it would be an easy test to see if this is just the switch?

Although if just the switch, it makes one wonder why the rear fogs have stopped working too.

...interesting. More to follow once I perform some tests/checks. But any initial ideas based on the current observations are much appreciated.



P.S.

Although in another thread I was asking about testing after fitting a Canadian Body Processor Module, I should clarify that I have not done that yet. The original BPM is still installed.


.

 

Reference for the rear tail light bulbs:

 

Hi Al,

If you don't already have it, you can download the 1997 X300 Electrical Guide here:

http://www.jagrepair.com/images/Auto.../jagxj1997.pdf


I doubt all of your outages could be due to just one fuse, but they may all use the same ground/earth point. They could also all pass through the same fusebox where a cold or broken solder joint could be the problem. Or, a loose or corroded electrical connector.

As far as the schematics show, the Brake Switch connects via a Purple/Blue wire to all of the following:
Transmission Control Module
ABS/Traction Control Module
Cruise Control Module
Lamp Control Module (Stop Lamps)
Body Processor Module (Gearshift Interlock)


The Black wire from the Brake Switch goes to Ground/Earth

Cheers,

Don

 

Hrmm, something else I just recalled.... I pulled out the trunk lining to remove and work on the CD changer before this happened. I wonder if there is a connector I've knocked loose when I pulled out the lining.

I'll update if I find anything....

.

 

OK, solved it... yep it WAS the stupid LED lights I was testing in the high mount brake light. They kept blowing the 10A fuse in slot 14 behind the right heel board fuse box.

Tested several times and confirmed.

I guess the LEDs I tried are quite high current. Ah well, won't be using those.

Good news is no bad rear bulb module, but I still think I need a new brake switch as it is intermittent. So that's still on the list.

.

 

BTW, here are some the "cheat sheet" notes I gleaned and compiled from other "brake lights out" threads... in no particular order:

And: https://www.jaguarforums.com/forum/x...6420bb-148637/


.

 

Al,

I went to re-install the 3rd brake light this morning. Nothing. No brake lights at all.

Odd thing was, I had "up-grade" to LED bulbs also.

Came searching the forum and found this post.

10A fuse in slot 14 on Right side heel board.

I think we think alike.

 

Help! My Reverse light and all Brake Lights stopped working... I went to four workshops but they all could not find what is the problem, what made it worse was the cigarette lighter stopped working as well after I left the last workshop...

I’ve tried the many ways suggested in the forum, cleaning relays, checking all the fuse etc...

They suggest that I leave my car there for them to trace the problem. I wish I can narrow down to the possibilities so I can suggest to them.

I’ve also tried the many ways suggested in the forum, cleaning relays, checking all the fuse etc...

I’m so lost now

 

Hi Huat,

Diagnosing the type of fault you describe is not usually difficult, but we can only guess unless you let us know the year and model of your Jaguar since the electrical circuits and controls can vary significantly. It's a good idea to add the year, model and engine info of your Jag to your signature line. Go to your User Control Panel and look for Edit Signature in the menu on the left.

Cheers,

Don

 

Hi Don,

its a Jaguar XJ6 3.2/ X300 / 1996, I’ve included it in my signature, thank you!

 

Hi Huat,

You can download the wiring diagrams for your car at this link:

Jaguar X300 Electrical Guide 1996

The power for the brake and reverse lights is supplied by the Lamp Control Module and all lamps are grounded at the trunk ground point at the right rear corner:



I would start by cleaning that ground point and then checking for power to the lamps and working my way upstream using the Electrical Guide until I found the failure point. It seems logical to assume the failure point is common to both tail lamps.

Cheers,

Don

 

Hi heres an update,

I have arranged an appointment with a workshop for this morning to troubleshoot the problem, but very very strangely, the car is back to normal last night with all the issues gone! I drove my car today and also no more problems. I had to cancel the appointment with the workshop, cancelled my booking for a rental car. I hope the problem will not come back. But this is so strange to me, did or can the car computers rectify the problem by itself?

 

I’m a happy man today.

Today, the brake lights, reverse lights and cigarette lighter power went off again. I seeked the help of a friend, not a Jaguar specialist but knows about electrical. He went straight to the rear right passenger fuse box, knocked it while the gear is engaged to R, the reverse lights turned on and went off. So the culprit is the fuse box, not the fuse, not the connectors to the fuse box. As there are no new or old fuse box available, he went on to do his magic, soldering the fuse box. All ok now! Problem solved! Woohoo!

Its solved and I thought I should update this thread about how I solved my issue so it benefit the rest for the many years to come.

Cheers

 

Excellent result and thanks for updating !

 

Just an update again. Apparently soldering by an electrician had some mistake and I thought the problem was solved. The cigarette lighter power always stay on even when the car is switched off. So ever since I’ll unplug everything on the cigarette lighter when I leave the car. Now during the lock down, I’ll drive or run the engine for about 10-15mins. One day when I skipped a day, the battery was flat. I changed a new battery. I started to suspect something else is draining the battery besides the cigarette lighter power socket, and I found that the centre console clock is still on after I switched off the power (its blocked by the single din flip up screen of the headunit). So i guess the soldering error also caused the clock power to stay on. I then changed the fused box with another used one I got from ebay. Solved the cigarette lighter and clock staying on issue, but the brake lights problem surface again, no brakes light, no third brake light. So I suspect since the beginning the problem
could be the connectors to the fusebox. I sprayed contact cleaners on the fusebox connector, the connectors of the car, and grounding points. Now the brake lights are back. Everything is fine now. I hope.

 

Several different electrical faults that might seem unrelated could have something in common... if you know "where" to look...

I had a similar problem years ago with my 96 VDP which was eventually traced to the RELAY in the right-hand heelboard fuse box. The relay was intermittent. Have you tested (or replaced) this relay? You can swap it with the left front (engine) fuse box relay (which is really only the horn relay).

The right-hand heelboard relay controls all the items attached to fuses 10, 12, 14, and 16. The relay switches power on to these circuits when the key is turned to ignition on. Check the fuse layout list in the engine compartment..

SORRY, NO DIAGRAMS. Troubles uploading the clipped pdf's.

The rear lamp control module, high mounted stop lamp, lighter socket (all F14), and clock (F16) run through these relay controlled circuits. Plus a whole lot more that might not have given any clue as to their correct or incorrect state.

Most likely your battery went dead because the relay stuck closed, and the side mirror heaters (F12) were on for a long time with the car shut off.

It is a very important relay since it also feeds the fuel pump relay through F10! That was the root cause of my problem long ago. Intermittent fuel pump/no fire up, while the rear lights failed simultaneously.