Bad Brake Light Switch?

Can't give you an answer to the problem, as it seems all 3 systems don't have a common link, except maybe poor ground. That's not to say a past owner did some creative wiring to the car that causes the problem.

However, the 93 manual has been added recently to the GM service manual thread. Good hunting.

So, I unplugged the tail light harness stepped on the brakes and dash lights don't come on. Guess that means there's a problem with the harness or someone put the wrong bulbs in the sockets.

The only time I've ever encountered a problem like that was on a toyota truck. The owner had wired in trailer light hook up using an American wire harness on a Asian type lighting system.

Because of the 2 different systems of lighting used between American and Asian, every time he stepped on the brake pedal the parking and running lights also came on.

So the only thing I can think of is to look for home done re wiring in the harness.

Sounds like you are missing a ground connection on one of the brake lamp bulbs or sockets. With no ground, the current flows through the brake lamp filament and then through the bulb's other (parking) filament to a ground on the parking lamp circuit. Dash lights are on the same circuit as the parking.lights so they light up also. I would pull out the brake lamp bulbs one-at-a-time until you find the culprit, then locate the missing ground for that one.

Yeah, I just need to get the time to narrow it down to which socket it's coming from but at least now I know where to start. If I remember correctly I think one of the sockets was replaced. Thanks,