I've been a busy bee with my '88 XJS over the last month. A few weeks ago, I had new (used) starfish rims put on. Left the car at the shop and picked it up a few days later. On the way home noticed that the kickdown switch was not working (which I had recently repaired) and neither were the turn signals. Once home, my wife said that my brake lights had not come on at all.

Quickly figured out the 7.5 amp fuse for the kickdown, turn signals, and brake lights had blown (why the kickdown is on the same line as those other two is beyond me). Popped in a new fuse, turn signals work great. Pressed the brake pedal and the fuse blows again.

Scratching my head now I figured I had a shorted bulb. Pulled all the bulbs and both driver's side looked a little sketchy and definitely the oldest. With them out, fuse does not pop. Replace bulbs with new ones, everything works and I'm happy.

Drive the car around every day for the next week without issue. Drop the car off about a week later for paint and body work. Picked the car up 10 days later (today) and brake, turn signals, and kickdown are once again not working. Sure enough, fuse blown. Replace fuse, blows again every time the brake pedal is depressed.

Now I'm wondering if there is a short in the wiring somewhere. Disconnect the wiring going to the brake lights on top of the boot (assuming you guys with coupes have those lights inside the rear windshield). Sure enough, fuse no longer blows. Look at the wiring and visibly looks fine. Scratch my head, reconnect the bulbs on top of the boot. Brake fuse no longer blows. What the heck?

Any ideas? I really didn't do much to the wiring either time... my first thought is an intermittent short somewhere, but possibly something goofy with the relay?

Cheers,

- Will

 

How much of the wiring were able to visually inspect?

How does the lamp socket look?




Leave it disconnected for a few days and see it the fuse *remains un-blown*. Shorts circuits can be tricky (as if you didn't already know!) and the fiddle-factor can lead to false positives and negatives (no electrical pun intended)



It doesn't take much.



I agree



Not sure about the converts but the coupes didn't use a relay in the stoplamp circuit and the upper lamp was semi-divorced from the main brake lights.

Cheers
DD