1990 Daytona Shelby Pass Side Brake Light NOT WORKING!

[90Spirit2.5]

Okay. Every function in the tail lights work EXCEPT the pass. side brake function. I have twelve volts on the RH brake/turn signal lamp wire when the brake pedal is applied...ONLY when I have the harness connector unplugged from the RH tail light sub-harness. Once I plug it in, the twelve volts drops off to zero. There is not a short in the RH sub-harness, I can take it and plug it into the LH harness connector and and all filaments function properly. So, I am wondering what to do here. The problem isn't in the turn signal switch either, I have completely removed the turn signal switch pod and the RH brake function still doesn't work. This wire(brown w/ red stripe) is a shared wire for the brake function and the turn signal function. The turn signal function works perfect. But the second brake pedal is pressed with all harness' plugged in, the voltage immediately cancels out. But the RH turn signal still operates fine when the brake pedal is pressed. Please someone lead me in the right direction. I'm stumped. Thanks for reading.

[cordes]

It's probably the ground at the bulb they go bad on most of the cars in my experience. I've read that the ground is the thing to look over when you lose voltage when load is applied anyway, so that's where I would start.

I ended up soldering in a new socket into the harness in my shadow for this very reason. The ground fails right where it meets the bulb socket deal.

[90Spirit2.5]

I replaced all four brake lamp sockets on this car hoping that the sockets would fix the problem. I used the sockets from the front of a 2nd gen caravan. Much nicer sockets in my opinion.

[cordes]

I replaced all four brake lamp sockets on this car hoping that the sockets would fix the problem. I used the sockets from the front of a 2nd gen caravan. Much nicer sockets in my opinion.

Interesting. Try running a separate ground for it as a test. If it doesn't die when load is applied you'll know you need to fix the ground.

[RoadWarrior222]

Unplug the tailgate harness, see if it still does it... if so, it be a short in that, 99% likely at the hinge.

[90Spirit2.5]

I ran a long jumper wire from the battery + to the RH brown/red wire in the connector and the brake filaments illuminated. I also tried running that jumper wire from the battery - to replace the ground feeding the RH tail light sub-harness, and the problem still exists. So, the problem is not a bad ground. And it is not a a bad ground connection in the sub harness or sockets either because when I plug the RH light assembly into the LH harness all lamps/filaments function properly. I also tested voltage with the two RH brake lamps out of the sockets(with everything hooked up like it should, stock wiring) and the voltage remained present. It isn't until one or both brake lamps are plugged into the sockets that the power drops off. But, when running the jumper lead from the battery, there is voltage with or without the lamps plugged in. Again I return to my conclusion that something is wrong with this brown/red power wire up in the dash. Turn signal switch is not the culprit, I tried switching that out with a currently functional unit from another car.

[90Spirit2.5]

PROBLEM SOLVED! It was the relay for the RH stop/turn signal.

[cordes]

Glad to hear that you solved the problem. I'm sure this will help someone in the future.