Brake Light Gremlins

[Opelupogus]

A few days ago I started up the Opel to show off my recently installed sprint manifold, ported intake, and 2" exhaust. However, my neighbor was more entertained by the brake lights that turned themselves on and off as though the car was possessed by a demon. The brake lights were on when I started the car, after about 45 seconds they turned off - then on again a bit later and off ... you get the picture.

I searched on the forum but did not find much information - is this a brake switch issue or should I be looking for the problem somewhere else?

--Bruce

[newman27]

It sounds like these things happened while the brake pedal was not in use. What happens when you actually depress the brake pedal?

The first thing I would check is for a loose bulb in the socket. I had two lights that were intermittent (one turn signal and one license plate light) and both ended up simply being a case of vibration moving the bulb around in the socket. I added some grease and set them back into the socket firmly and both have worked consistently ever since. Of course brake lights shouldn't come on with no pedal activation so this may not help but I would check anyway. Next, I would check the ground wires to the body for a loose screw. Finally, I would check the brake light switch itself under the brake pedal. I've replaced one of those a long time ago - it is a tight fit but easy to do. I think these are the three simplest places to start. After that, I guess you need to trace wires for a bad connection which is more involved.

HTH,

Matt

[BMWonly]

Also, check the brake pedal return spring. If that's missing or not installed correctly, the brake lights can come on and off even without touching the pedal.

[Dennis Texas]

brake lights were on when you started engine? Unless you had your foot on the brake sounds like a faulty switch. Check across it with a meter. Then start looking at gorunding wires and bulb issues.

[Dennis Texas]

Originally Posted by BMWonly Also, check the brake pedal return spring. If that's missing or not installed correctly, the brake lights can come on and off even without touching the pedal.

yes something along those lines is a good place to check

[hrcollinsjr]

Originally Posted by BMWonly Also, check the brake pedal return spring. If that's missing or not installed correctly, the brake lights can come on and off even without touching the pedal.

Seems like most of the GT's that I've fooled with didn't have brake pedal return springs. It was only an issue with one car. Someone following asked me if I was resting my foot on the pedal because the light kept coming on at odd times. Searched my parts cars and finally found a return spring. Fixed the problem.

Harold

[Opelupogus]

Thanks for the suggestions.

First - the brake pedal return spring is in place.

Second - I turned the key without starting the car (because the kids are sleeping) and the brake lights were not on. However, the slightest pressure on the brake pedal causes the brake lights to turn on.

Bare with me while I break out some crazy logic - brake pedal is connected to the booster that is connected to manifold vacuum right? If manifold vacuum pressure is changing (ie fast idle to slow idle) the pressure on the brake pedal may be changing slightly too. Since it only takes a small amount of pressure to activate my switch - are fluctuations in vacuum pressure due a few 100 rpms enough to cause the brake lights to turn on and off?

If so - is there a way to adjust the brake switch?

Thanks,
--Bruce

[timemachine]

I don't want to outthink your theory, and you can check the vacuum line from the booster and look for other leaks, but I'd start by looking at what appears to be a mechanical/electrical problem. The return spring on the GT pedal is designed to bring it to a stop at the same time the square metal plate attached to the brake pedal is holding the switch open.

Unlike Mantas, I haven't found the brake switch on my GT to be adjustable, though you could bend the tab on the brake pedal to bring it more into contact.

Your test seems to show that the pedal works normally, but the lights come on occasionally by themselves. To me that suggests your switch is just on the edge of closing, (which you can adjust by bending the tab on the pedal), that you have intermittently shorting contacts behind the switch, or that the brake light switch is intermittently shorting on its own. The last two would be pretty unusal.

I'd start by seeing that the brake light switch is securely screwed into its bracket, then see that the pedal returns fully to it's stop at its highest point. After that, I'd bend the tab on the pedal that contacts the switch slightly backwards to bring it more into contact with the switch. After that I would test and/or replace the switch.

Let us know what you find out.

Jim

[Gordy]

I had the problem where every time I would push in the clutch to shift my brake lights came on for a moment from the pressure of pushing in the clutch (it is on the same through bolt as the brake pedal). My guess would be you just need to bend the tab to keep more pressure on the switch button.

[jlthunder]

Originally Posted by Gordy I had the problem where every time I would push in the clutch to shift my brake lights came on for a moment from the pressure of pushing in the clutch (it is on the same through bolt as the brake pedal). My guess would be you just need to bend the tab to keep more pressure on the switch button.

I have the same problem. Thanks for the reminder. I will look for the spring and bend the tab if needed.

[Opelupogus]

Last night I bent the brake pedal tab slightly and just as everyone here had predicted - the problem was solved.

Thanks,
--Bruce