Fuse is fine, relay replaced in rear, (original tested fine) replaced bulbs, (originals tested fine).

Took off the brake light switch from the brake pedal, cleaned but was not sure how to test.

I can apply power from a relay in the trunk and all 3 light up.

Would like to apply power at the connector from brake light switch but unsure how, 4 wires??

Found schematics on line but hard to follow.

Any help would be appreciated, I have wasted several hours as I am a fool when it comes to trying to track down a problem!!!

Cal in AZ
94 XJS Red Ragtop 4.0L 65k

 

Have you checked the brake switch, located above the brake pedal, under the dash. If you google "1994 jaguar xjs brake switch", the part will come up.


Not a cheap part, but you should be able to diagnose it.


Disconnect it and jump the Light Green/Yellow wire with the yellow/red wire or the Green/Black with the Black wire and you should see results. (Just make sure power to the car is on)

 

That's what I was looking for! Jumping it should activate brake lights, will try possibly this AM or tomorrow, Cal

 

That stock brake light switch is pure JUNK, no other way to put it, Curly, Moe & Larry must have designed it. I think Kirby adapted up a plain old button type in his Book but not sure. I,m sure others have. I know that's in my plans . Maybe someone will tell us how they did it.
Lawrence

 

So the 2 blacks light it up like Xmas tree, yellows do nothing. Wow!!

Why so many wires for that switch?

So it could be the brake light switch? please comment.

A homemade switch?? Got a link?

Thx, Cal

 

I believe that the Green/Black and Black wire should light up the third brake light. The two tail lights should not light up with those two wires shorted.

 

?????
I'm on my 5th XJS and never had a problem with the brake light switch on any of them.

 

All three were lit with G/B and B wires, nothing with the G/L and R/Y wires.

Will test again, is plain Black a ground?

Should any other combinations work?

Thx, Cal

 

Plain black is ground.


Maybe I'm wrong. There's a wiring diagram you can reference on


http://www.jagrepair.com/images/Elec...Electrical.pdf

 

I have that wiring diagram, page 25 Fig 6 shows only 2 wires going to the switch.

Black and Green/Black, no R/Y or G/Y wires.. they are a mystery to me.

RH113 relay says above ABS unit which I replaced, tested old one fine, in the trunk, nearly impossible to get at.

Will pull the switch again and test now that I know the B..G/B relationship.

Keep the thoughts coming! *480*278*9148*

Thx, Cal

 

I've replaced 4 in the 20 years working on XJ-S's. I'm on my second and the other two were jobs of other owners car's. I forget the switch cost, I bought two through Walsh Jaguar (used) & two through $Dealers$. I do know if removing the pedal box is planned (for any reason) I would remove the switch as my FIRST move and the last thing to put back once the box is in place.
Lawrence

 

If you have cruise control, then it could be that two of the wires disable the CC when the brakes are applied - this will be achieved somehow by the system. A careful look at the diagram (if you have a complete one for your exact model) should enable you to follow the unidentified wires and see where they end up. There are other possibilities, eg cannot raise hood with engine running unless foot on brake, cannot start engine unless, etc etc.
Greg

 

My XJ wuzza six is nt exactly the same, but quite similar.
a kind motorist told me of no brake lights.


In my car, there are two behind the pedal. One for the brake light that
closes on application and completes the light circuit. It is powered from a nearby fuse panel. that panel is in turn powered by the ignition switch. I found no juice on that fuse panel. Much travail later, a replacement ignition switch restored t. a lot of things began to work!! I changed the switch, an awesome task, simple in execution, it is the location. Upside down was never easy, got much harder as he years past. I found the switch to be quite decent. Not junky as others have opined.


CAVEAT. As in many Jaguar things, the ignition switch must be on for stuff like brake light to work.


2. The other somewhat similar switch is the cruise interrupt. It opened on pedal application. if the cruise is on, it is shut off by braking. Reverse logic in the two switches.


Carl.

 

That makes sense, it does have Cruise, never have used it but that explains the wires!!!

I will pull the switch and check again, will send results when I get back next week.

Great info, thx to all!!

Cal in Phx

 

Ground the Green/black wire and the stop lights should come on.

The green/yellow and yellow/red wires are for the cruise control stop switch. When you touch the brake, the cruise will disconnect, that switch is what interrupts the cruise.

 

UPDATE!!! turned out the switch on the brake light was a fraction out of line. The little red tattletail on the switch moved but not enough.

The holes on the switch are much bigger than the little studs so was just slightly out of line. Found some more small lock washers and secured.

Crappy design but working now.