On my 1994 the normal operation of the rear combination brake and turn signal indicator lights is to light (brake) or flash (turn indicate) the bottom two bulbs in the four light cluster.

My left light cluster works as expected. When pressing the brake, both bottom bulbs light, and when using the left turn indicator both bulbs flash.

On the right cluster, when pressing the brake both bottom bulbs light as expected. BUT only the left most of the bottom pair lights & flashes, and the right bulb does not. I have swapped bulbs with no change in faulty function for the right socket.

Beyond the simple bulb swap, I've admittedly not done any other troubleshooting. The XJ40 is new to me, so just starting to figure out how it's built.

What's interesting is that all of these bulbs are single filament bulbs, so the multi function (stop and turn) are clearly controlled by some relay or module versus wiring in the socket or even perhaps the tail light bulb board itself. So that worries me a bit that it may not be something simple.

Any thoughts on how best to approach identifying where the fault lies?

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I had the same problem, traced it to a cold or cracked joint on the circuit board at the rear of the socket - posted a thread here about it I believe, I'll take a look to see if I can find it ...


here it is


https://www.jaguarforums.com/forum/x...-light-189992/


Larry