Why does my brake light keep coming on? I blead my break lines. Got the light to go out for a couple of days, but back on now. Checked brake pads, a good 50 precent left. brakes seem a little mushy, not bad though. Resivior not loosing fluid. Any guidance would be appreciated.

Skid63

adjust the brake light switch under dash..

crawl under dash..

find switch that contacts brake pedal arm

adjust it more towards the pedal

You could be getting some air pumping in if you have any rotor run-out exceeding .005". This is a real common problem with the calipers used on our vettes. A partial fix is to replace the calipers with the stainless-sleeved O-ring design. The real fix is to correct the run-out and also do the calipers.

Not sure about a 75, but on my 72 there is a brake pressure switch on the distribution block that is mounted to the frame almost directly under the master cylinder. It may be mounted to your master cylinder on a 75.

Either way that switch could be bad. Have a loose connection or the wire could be shorting out which could cause the light to come on.

It could also be the switch under the brake pedal, but if memory serves me correctly I thought this switch is designed to make the brake light come on only when the pedal is pushed to far to give warning of a low brake pedal.

Is the brake light coming on and staying on when its first started? Or after you have been driving it for a while?

Does anyone know if the parking brake has a switch on it that might make the light come on?

the parking brake should not activate the brake lights

if it did... everytime you parked you car youd run down the battery.. there is a switch but it is a dash light indicator.

I had my brake lights come on every once in while when I was parked on a down hill slope.. the brake light switch was gapped out in too far and the return spring was kinda weak just adjusted the switch and never had it again.

it may be quite different on something as "new" as a 75, the electrical system cahnged quite a bit from a 69

I think he means a brake warning light on the dash.

And the brake warning light on the dash has nothing to do with the rear brake lights.

It is activated by two things. One is the parking brake. There is a position switch on the base of the parking brake lever.
The other is the pressure switch on the pressure valve, often part of the gang/perportioning valve. This monitors the front/rear pressure of the brake fluid from the master cylinder. If the pressure is not equal, the switch will move position and the light will come on. Newer cars also have a brake fluid level sensor, but not our C3s.
If you loose brake fluid, or there is air in the lines, or one caliper is pushed back too far and won't build pressure on a brake pedal stroke, the light will come on.

You could also have a grounded wire in the circuit. The light has power at all times the key is on. It is turned on by suppling a ground to the light. All of the above create a ground. If the wire is pinched or touching ground anywhere, the light comes on. A pinched wire is not likely unless the interior has been recently worked on. The park brake switch is the most common fault. It gets filled with crud, and won't open when it's supposed to. Or the park brake does not relax all the way down.

If you pump the brake pedal several times with the car sitting still, and the light goes out, it's a hydraulic related problem. I say related due to the fact a loose wheel bearing allowing a rotor to move could do the same thing. It could be hyd. and not shut off the light this way, but if it does it's certain.

After Shark said: ..... Does anyone know if the parking brake has a switch on it that might make the light come on?

this is what i replied to..

should have quoted it the first time..