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'91 GMC Air conditioning problems.

Discussion in 'General Chevy & GM Tech Questions' started by jackal, Jul 9, 2011.

  1. jackal

    jackal New Member

    My air has always worked well but the compressor always made what i call a groaning noise when it operated and I could hear this inside the truck. I have owned this truck since it was a year old. Once in a while the AC would flash on the heater control and I would disconnect the battery and reset and it would work again. Now the AC doesn't work at all and the AC flashes every time I start it up. Is this more than a recharge problem?...is it worthwhile to try to fix?...thx
  2. stephan

    stephan Rockstar 4 Years 5000 Posts

    If it's lost enough freon that it won't engage the pressure switch then the compressor won't run at all.
    I wouldn't fault the compressor just yet, as mine has growled & knocked for 9 or 10 years. You can do a quick bridge of the pressure swtch (should be on the rec drier by the firewall) & if your ac clutch kicks in, then it's just low on freon.
  3. MightyMax

    MightyMax Rockstar 100 Posts

    If the A/C is blinking, that is a signal that the pressure is not right.
    So adding in more Freeon should correct that problem, once enough is in there, it can get its pressure right.

    I have had some loud noises from the compressor on mine....to the point I thought it would blow up and shoot through the hood of my truck....
    I went and added in some more Oil last night, and I think I have corrected the issue....
    I need to take it out for a drive and test it, but I hope I have corrected the problem.
  4. SURFROGGY

    SURFROGGY New Member

    How do you add oil to the AC system?
    Last edited: Jul 13, 2011
  5. MightyMax

    MightyMax Rockstar 100 Posts

    You will need a set of guages, and then go down and buy some pressurized oil at Adv. Auto or something, and add it in like you would R134
  6. jackal

    jackal New Member

    tried to bridge the low pressure switch, but no go...the compressor will not fire over...now what?
  7. Revredneck

    Revredneck Rockstar 100 Posts

    You have to reset the control head by unplugging it or disconnecting the battery cable first, then you can jumper the connector to see if it will work.
    Good Luck and God Bless
  8. jackal

    jackal New Member

    I noticed that the high pressure schrader valve was hissing slightly..fixed that, disconnected battery, jumped the low pressure, reconnected battery, started vehicle and set air to high and dumped a couple cans of super secret R-12 and I'm cold....thx everyone
  9. danomt

    danomt New Member

    Information on 91-92 gm c/k trucks gm bullitin (92-201-1b) problems with false clutch cycling would set of the a/c flashing light. GM would have you remove the a/c control had and disconnect the dk green circuit wire. this disables the low charge detection system. This only applied to 91-92 c/k trucks. tks, DanO

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