compressor clutch will not engage

Discussion in 'The Big Chill' started by xraylee, Nov 19, 2010.

  1. xraylee

    xraylee Well-Known Member

    I am trying to replace ac on my 71 skylark. The original parts were removed by previous owner. A compressor, dryer, condenser have been installed. The fan works but the compressor does not engage unless the contacts are jumped. What is missing? Thanks.
     
  2. Dylan

    Dylan Murphy's Law Is In Effect

    Is the refrigerant charge low? If the pressure is too low the AC compressor clutch won't cycle.
     
  3. 71skylark3504v

    71skylark3504v Goin' Fast In Luxury!

    Sounds like a simple electrical problem. Trace your compressor wires back until you find the problem.
     
  4. idahoskylark

    idahoskylark idahoskylark

    if your jumping the low psi switch on the drier then either the switch is bad or you need more freon
    was it charged after it got put back together
     
  5. xraylee

    xraylee Well-Known Member

    Yes, The system is charged. Thanks. Also, I was jumping it by running leads straight from the battery to the compressor to see if it would engage and it did.
     
  6. xraylee

    xraylee Well-Known Member

    Also, for some reason now the fan from blower motor is intermittent. With fan turned on in any position sometimes it will not run and then while running down the road and come on by itself and will stay on until the next time. I am wondering if the expansion valve is clogged because I did not change it.
     
  7. lsrx101

    lsrx101 Well-Known Member

    Does your 71 have a Thermal Limiter Fuse? It would be a small box in the compressor harness near the compressor. I don't recall exactly which cars used them.
    If the compressor was run with a low system charge at some time in the past, it may be blown.

    The wiring for the compressor circuit is fairly simple but some GM cars of that era had a shutdown relay incorporated that would engage the comp. briefly when the engine was turned off to prevent dieseling. Again, your car may or may not have this.

    A wiring diagram would be a big help. Something like this, maybe?
    http://global.ebay.com/1971_71_Buick_Sklylark_11X17_Full_Color_Wiring_Diagram/360319986282/item
     
  8. John Eberly

    John Eberly Well-Known Member

    Intermittant fan would not have anyhing to do with refrigerant charge.

    Idon't know if '71 had a low charge pressure switch. My '68 does not - just a switch on the fan control that feeds power to the AC/Defrost positions on the function switch. Both need to be made to get the clutch to run, and I just discovered that one of them is broken on my control.
     
  9. Steve Craig

    Steve Craig Gold Level Contributor

    Compressor will only come on with fan in XX position. Check for grounds at the fan & the compressor. The "intermittent" is leading me to think you have a loose connection somewhere.
    The big cars with auto AC had a switch on the rear of the RH head. Delayed the fan until the engine was warmed up. Didn't want cold air blowing thru the cabin on a cold day.
    '71 Chassis Manual is about the best money you can spend if you don't have one now.
     

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