I was cleaning my car yesterday and have discovered that my tail lights are not working correctly. When the light switch is off, they work great. When the light switch is on, the reverse and turn lights are on but very dim. When I turn in the turn signal, the opposite sides lights blink and the license lights blink. I have checked all the fuses that had anything to do with the lights and all are good. Is there something else that controls the tail lights? I have a great shop that I can take the car to, but if this is something simple I'd like to take care of it myself. Also, when the light switch is on, the right tail light does not work, but if I turn the switch off and press the brake, the light works. Any help would be appreciated and if this sounds like something a dealer should see I will take it in.

 

hi, years ago these symtoms used to be due to an earthing problem, at that time it was just a case of finding the earth connection on the light cluster and running a new wire to a suitable earth point.
You could even just temporarliy hold a piece of wire across from the light unit to an earth point first before actually joining it in properly.A good temporary earth point could be the boot/trunk latching bar in the middle.
You may find that simply finding the earth point and cleaning the connection point up might help.
It used to be quite a common problem but I have not seen the problem on a Jaguar before.
Concidering they do suffer from earthing point problems behind the headlights then they could also have issues at the rear lights !
Best of luck

 

Exactly.

 

Did you ever find a solution for this? I have almost exactly the same problem.

 

There is a rear electronic module in the right side of the trunk. The lights in question are routed through there. First check for corroded connections, from there, it gets to testing and you will need some serious documentation for the pinout tests. I use Alldata.com for things like this. Just get a subscription and jump in!

 

That's the classic 'bad earth on the cluster' fault.

 

You are correct a bad earth ground would be the first place to look. Pull the plugs on both your lights and see if you have any evidence of a hot spot on the terminals first.