Hi, I have a weird issue with my XJ 1995. Tail lights work when park- or headlights are turned on and ignition is in OFF-position, but when I turn ignition to ON, tail lights go out (but headlights still work).

Brake lights, blinkers, dim lights work fine. Just the tail lights turning of when I put the key in ON-position. Any ideas? Bad head light switch? Any help is much appreciated.

 

If it just started doing it, I'd say HL switch would be a good place to start. I couldnt tell you how to verify it with a multimeter though.

 

I think the ignition switch is a more likely culprit - although, must confess, not sure how/why.

 

Is there any dimming at all to the other lights? So for example, put your tails on, press the brake pedal, put hazards on, with ignition on, put reverse on. Do all lights work together at the same time? Try again minus the brake light and are your tails doing anything or completely dead?

From the 95 diagram there isn't really any link between the tail lights and ignition switch so this may be tricky to track down.

 

That is true, & what I'm struggling to understand. However, there is a link between the ignition & tail light housings, as reverse lights & turn signals only work with ignition on, so, if there's an short within the housing, but not to ground . . I think you might be onto something with checking various permutations & combinations. Think I'd start by isolating one side & concentrating on the other, just to eliminate some variables.
It's likely going to be a long, tedious procedure, but I can't see any alternative.

 

I do it at work all the time on the refit phase of a restoration, it easily highlights a bad common ground or individual bulb grounds. In this case it may highlight which circuit is causing the funkyness.

 

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wtf ?

 

AI - with no calendar function