Brake light problem Help

[onefastgn]

They work when the car is shut off but when its running the brake lights do not work but the window one comes on still when I apply the brakes even if its running or off I just don't know where to start to look to fix the problem I've even tried it with the lights on but it still won't work any suggestions...Thanks

 

[BlackBeauty]

This may sound strange, but with someone watching the brake lamps, apply the brakes and wiggle the turn signal in all directions.
Not even sure if this applies to GN's, but some GM vehicles have the brake lights wired through the turn signal lever (since on some vehicles, the brake lights also act as the turn signal lights). The 3rd brake light, which you mention is still working, is not wired through the turn signal lever.
The strange part about your situation is that they work with the car off but not on... never heard of that. Good luck.

 

[onefastgn]

Thanks I was just messing with it again and now I can get it to work with the car running but they sometime quit working But with just the key on the on position I can hear the pump or somthing making a wizzing noise every time I pump the brakes.I always hear that sound every time I turn the ignition on just before I start the car but What I'm wondering is why it keeps sounding like it missies then stops and then wizzes again and again. It sounds like th E-H pump is bad or the Switch Is bad or somthing Hell just one of the tail came on and As I was still pumping it The other one came on I just don't know.Guess I will try again tomorrow Thanks again I will still try what you said you never know.

 

[Turbo Brian]

The brake lights are wired through the turn signal switch. There is a white wire at the bottom of the steering column that runs from the turn signal switch into the harmonica connecter. This is where the turn signal switch connects into the body harness.

There is a sharp turn at that location and usually the white wire at the bend of the turn has worked its way loose in the connector.

This is a common problem, I have seen lots of G body cars in the salvage yards with this same problem.

The fix is to repair the connection at the harmonica, or simply use a butt connector and connect the two white wires (outside of the harmonica connector).