My tail lights dont work when i turn on my headlights for a 91 gmc sierra

SOURCE: 1998 GMC Sierra Signal Fuse Blowing

it seems you have a short in either one of the lights or interlock. all are connected to the same fuse. trace the wiring from the fuse box back to the component. Using a test light test in between the wires. check for any obvious breaks in the wiring.

SOURCE: 1985 gmc sierra truck headlights wont work. its not the bulbs

well we just fixed our truck it was a wire that connects to the starter had some out! might want to see if there are any wires disconnected there

SOURCE: Tail light problems on 1996 GMC Sierra pickup

I had similar problem with my 97 sierra... I only lost 1 light, then brake lights stayed on all the time... turns out the "t" connector for the trailer harness under rear bumper was rotted inside...unplugged the 2 parts of the harness and pluged them into each other with out the "T" harness.... everything works great... Hope it helps ya

Dennis Mulford

• 1055 Answers
• Posted on Jun 06, 2009

SOURCE: No brake lights, or no signal lights

brake lights and turn signals work off the same curcit, it could be the fuse or the brake light switch !!!!!!

SOURCE: tail lights work on both sides. turn signal and

check fuse to driver side turn signal lamp.check brake light bulb or replace bulb on driver side.also replace the front driver side turn signal bulb that is flashing fast.