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Thread: Brake Light Problem

  1. #1
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    Brake Light Problem

    The brake light on my '78 R80 no longer works with the front brake. It lights fine with the rear brake, but not the front. I cleaned the contacts on the switch, but that did not help. What should I check next?

  2. #2
    Benchwrenching PGlaves's Avatar
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    Quote Originally Posted by tlcoulter View Post
    The brake light on my '78 R80 no longer works with the front brake. It lights fine with the rear brake, but not the front. I cleaned the contacts on the switch, but that did not help. What should I check next?
    Trace the wires from that switch to where they connect to the main harness. Then disconnect them at this location and use a continuity testeror multi meter set on the Ohm setting to directly test the switch. Lever not pulled should read open or infinite ohms and lever pulled should read continuity or a very few ohms. If not the switch is bad.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://www.bigbend.net/users/glaves

  3. #3
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    If your switch is the same as mine, sticking out of the back of the master cylinder, short a screwdriver across the terminals and see if the brake light comes on. If so, replace the switch.

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    Quote Originally Posted by cseltz View Post
    If your switch is the same as mine, sticking out of the back of the master cylinder, short a screwdriver across the terminals and see if the brake light comes on. If so, replace the switch.
    Well, I don't know whether to say it passed the test or it failed the test, but the brake light did come on when I shorted a screwdriver across the terminals. When I replace the switch do I have to drain the brake fluid?

  5. #5
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    Quote Originally Posted by tlcoulter View Post
    Well, I don't know whether to say it passed the test or it failed the test, but the brake light did come on when I shorted a screwdriver across the terminals. When I replace the switch do I have to drain the brake fluid?
    Make sure first that there is no obstruction (sludge, etc.) preventing the brake pressure from triggering the switch. I would clean it up first, and make sure no obstruction, re-install and test to see if it works. It may still work.

    Could save a buck.

    Yes, I think you will have to re-fill the master cylinder with fluid and bleed out the line.

  6. #6
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    Suggest that you thoroughly drain the system and take care not to get any brake fluid on anything. The switch is not expensive but I had to take the master cylinder off in order to get the old one off and the new one on. That hose clamp will not be up to the torque. Brake fluid should be replace every year or so anyway from what I understand.

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