Hey guys,

I've got a strange problem on my hands. My buddy was following me down the highway the other day, and told me all of my brake lights were out except for the high light on the hatch. At first I didn't believe him, but I checked, and it's true.

I have nighttime running lights, turn signals, and hazard flashers, and the high mount hatch light works. However, none of the lights in the lenses themselves come on when I hit the brakes.

Has anyone had a similar issue as this before? I checked the fuses and they were good. I'm thinking there's possibly a bad ground or connection after the split between the high mount wiring in the hatch and the taillight wiring in the body. Anybody have a clue where to start looking for that?

Thanks,

-cal30sniper

 

I would start by checking the bulbs to see if they're bad.

 

Correct me if I'm wrong, but aren't those just two filament bulbs? One filament for the running lights, and the second brighter filament for turn signals/brake lights/hazards. If the bulbs were bad, none of that would be working. I'd also find it very hard to believe that all the bulbs went out at once. I know for a fact they were working 3 weeks ago, because I followed my friend home while he was driving it.

 

Not forsure how the rear lights are setup for turn signals, brakes and parking lights for trans ams. I know on my iroc, turn signals are a separate bulb and lense and brake lights also use a different but same lense for the parking lights. Still doesn't hurt to do the easy check of the bulbs. You could of had one out at sometime after you seen that they were all working and when your friend seen that they were all out, the other bulb could off went out before hand. If you had a ground problem for the rear lights, you would lose all rear lights as they all share the same ground including the high mount stop lamp. What car are you working on?

 

It's my '88 GTA. I just spent about 30 minutes digging through the factory service manual wiring diagrams. Although the high stop light and the regular brake lights use the same grounds, they do not use the same power feed sequence. The high stop light is powered directly from the brake switch, where the regular brake lights have to go through the turn/hazard switch first before getting power to the bulbs. This allows the interrupt of the brake lights for the turn signal or hazards being on.

Which begs the question: has anyone ever had a bad turn/hazard switch lead to brake light failure? It's not shown as an option in the troubleshooting diagram, but it would seem to be the problem here.

I'm extremely confident its not the bulbs. There are four of them. I would find the odds astronomical that they all went out that quickly. I would pull and check, but its a pain in the butt to do that on a Firebird.

 

If the brake/TS filaments come on for the TS, then the bulbs, wiring, & sockets are all good.

If the 3rd brake light comes on when you push the brakes, the brake light switch is good.

If both of those things are happening, then you have a defective TS switch... remember, its job is to decide between the brake light feed and the TS flasher feed for the light that it's supposed to be making blink at any given moment. Sounds like its brake light feed contact is bad.

I agree with your diagnosis.

See my signature for help with logic and reason.

 

Thanks for the help sofa. AC Delco turn signal switch ordered and on the way.