Need help,! My 89 GTA blows the fuse instantly when I turn on the parking or headlights. I replace the headlamp switch, didn't work. I pulled the gauge cluster same thing. Unplugged the headlamp module under the hood same thing. The turn signals work and the brake lights. Also the headlamps will go up but not down when it blows the fuse. I can put a new fuse in with the lights off and they will go dow. Any help TIA Mark
Also the dash lights wont illuminate.

 

Sounds like there's a short on the tail light circuit.

Does it do this even when the headlight switch is unplugged? Anything else hooked to that circuit; aftermarket alarm for example? Have you tried unplugging the dash light dimmer module?

 

Most common cause of that kind of short is the illumination circuit to the radio has been cut to add an aftermarket stereo, and the electrical tape has fallen off, allowing the bare wire to touch ground and PAP! goes the fuse.

 

I will pull the radio tonight and see if that's it. The radio is out af a Yukon but didn't cut any wires. It was a direct bolt in.

 

Pulled the radio, no cut wires. Replaced the left fender blown bulb, no change. Where does the taillight harness plug in at? And are the side markers on the rear quarters only light up with the lights on or do they also double as a turn signal light?

 

found the guilty culprit! Blow back up light!

 

As so often happens, sometimes the simplest explanation is the one most likely to be right. Even if it's not the first one you think of.

Glad you found it!!