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brake lights flash on briefly, then go out when brake pedal is depressed

Discussion in 'GM Electrical Tech' started by markf1971, Aug 6, 2011.

  1. markf1971

    markf1971 New Member

    I searched extensively and found nothing related to my problem, so here goes my thread:

    I have a 1995 Chevy C1500 W/T 4.3L w A/T. When the brake pedal is depressed All of the brake lights (left, right, & third brake lights) flash on for just a half-second, then they go out even thought the brakes are still depressed. So, this doesn't appear to be the bulbs, or they wouldn't light up at all. Doesn't seem like it could be the brake light switch, or they wouldn't come on at all. I wouldn't think that the circuit boards would cause this either. When I laid down under the dash to look at the brake light switch, I heard a clicking sound when the brake pedal is depressed. The brake light switch looks like it would be a bear to replace, as I can only barely see it and can't hardly reach it either. I have not bothered to check my Chilton manual as I didn't think this kind of problem would be addressed in it. Sounds like a relay clicking, but I can't tell. I just figured the easiest and cheapest way would be to ask on this forum. I can use hand signals for now or just tap the brakes in rapid succession to let people behind me know that I am stopping, but I don't want to do that any longer than is absolutely necessary.

    Sorry I haven't checked the obvious like the bulbs, fuses, & circuit boards, but I figured that I wouldn't even be getting the brief flash if any of these were the problem. It also seems like if it were a relay that it would either work or not, instead of just flashing on for a half-second. Any help would be appreciated!
  2. Z71 Coltman

    Z71 Coltman Member

    Does how hard you press the brakes matter?
  3. markf1971

    markf1971 New Member

    No it doesn't matter.
  4. Z71 Coltman

    Z71 Coltman Member

    Check your wiring, sounds to me like a bad ground. pretty sure the ground for the brake lights is right near the light ass'y.
  5. sstoner911

    sstoner911 Epic Member 5+ Years 1000 Posts

    If its not a grounding issue as mentioned above, It may not be keeping the ground. When the brake pedal is depressed check the switch for power with a test light.
    Last edited: Aug 7, 2011
  6. markf1971

    markf1971 New Member

    I didn't realize when I started this thread that my 95 truck had a brake light relay; this is the first truck that I have owned that was newer than a 79 model, which didn't have a brake light relay. I checked the relay last night and swapped my AC & brake light relays. I'm still having the same problem with my brakes and my AC still works, so I believe that I have eliminated the relay as being the problem. I also found the source of the clicking that I heard under dash when the brake pedal is depressed. I found the part that clicked, yet I didn't know what it was called. Today I discovered that the name of the part, that makes a loud click when the brakes are depressed, is a Brake/Transmission Shift Interlock (BTSI) Solenoid. Does anyone know if this part can affect the proper function of the brake lamps? I don't ever remember hearing this part click before. If it did click before then I just wasn't paying attention or either I couldn't hear it. When I am lying in the floorboard and press the brake pedal it is rather loud now. Any help would be appreciated.
  7. nmc2010

    nmc2010 New Member

    you could have a short in your wiring somewhere. i had that happen to me in my old truck.

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