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Thread: NEED hydroboost brakes

  1. #16
    Join Date
    Oct 2004
    Location
    Charlotte, NC
    Posts
    8,159
    The pressure switch breaks ground to the pump motor when brake fluid pressure reaches a certain PSI (about 2300 psi)....

    Bad pressure switches usually will either cause the pump motor to not run at all or run all the time only when the ignition key is on.....

    If the pump motor runs when there is no key in the ignition, then the relay must be stuck in the closed position allowing power to go to the pump motor or you have something wrong in the wiring harness.....

    These units are not that hard to diagnose and work on....

  2. #17
    Join Date
    May 2012
    Posts
    55
    Yes also the rear brakes are not working as well

  3. #18
    Join Date
    May 2012
    Posts
    55
    I'd put my money on a relay before the wire harness, everything else appears to beclean and closed on it but yes still a possibility I suppose. So, so far it could be a pressure switch and accumulator. ?

  4. #19
    Join Date
    Oct 2004
    Location
    Charlotte, NC
    Posts
    8,159
    I don't think it's either....

    Check relay first, then you can go on from there....

  5. #20
    Join Date
    May 2012
    Posts
    55
    Relay was filled with water. No good

  6. #21
    Join Date
    Jul 2003
    Location
    Eastern (nee Western) PA
    Posts
    4,988
    Quote Originally Posted by the-big-e View Post
    The pressure switch breaks ground to the pump motor when brake fluid pressure reaches a certain PSI (about 2300 psi)....

    Bad pressure switches usually will either cause the pump motor to not run at all or run all the time only when the ignition key is on.....

    If the pump motor runs when there is no key in the ignition, then the relay must be stuck in the closed position allowing power to go to the pump motor or you have something wrong in the wiring harness.....

    These units are not that hard to diagnose and work on....
    Agrred. They are daunting to get your head around at first, but they last a good long time, they work well, and the simple stuff can easily be fixed.
    God bless!!!

    1990 SC auto ... red outside, gray cloth inside ... ~205,000 miles (and climbing) ... driven daily!

  7. #22
    Join Date
    May 2012
    Posts
    55
    Parts stores around me do not have the relay...

  8. #23
    Join Date
    Oct 2004
    Location
    Charlotte, NC
    Posts
    8,159
    Give me your zip code and I'll send you one for the cost of shipping....

  9. #24
    Join Date
    May 2012
    Posts
    55
    34608.. thank you

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