Question about Chevrolet C1500

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My dash mounted HVAC control unit in my 1991 C1500 Chevy truck suddenly lost power. I replaced it with two replacement units, but it still doesn't work. All fuses and fused links are good, and I have power at the plug in but the units won't light up and don't respond. What is my next course of action in repairing this problem? It's really HOT in Oklahoma in July!

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  • David Thomas Jun 26, 2009

    I back probed the power supply plug for the back of the controller unit. I have ground. The system charge is fine, just replaced the compressor, pressure switch about a month ago when I converted to R134a refrigerant. Used all new (not rebuilt) components.


    The AC was working fine on my commute home from work. One hour later my wife took the truck to town and said the lights flashed on the dash controller and it went dead. Hasn't worked since. My local shop briefly looked at it and tried a new unit with no success. The confirmed power to the plug and ground, then checked the fused links and fuses under the hood and dash.
    I have not checked the ignition switch, but if the plug is hot with the key on, isn't is good?
    Thanks for your help.
    David

  • David Thomas Jun 26, 2009

    How do I access the second power wire? What color and stripe is it and is it hot only with key switch on? Is it coming from the ignition switch?


    Thanks!


    David

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  • Chevrolet Master
  • 75,751 Answers

HAVE YOU TESTED THE GROUND, DO U HAVE A WIRING DIAGRAM? IF NOT GO TO ALLDATA.COM AND SUBSCRIBE, HOW DO U KNOW THWE SYSTEM IS NOT JUST LOW ON CHARGE?

Posted on Jun 26, 2009

  • 1 more comment 
  • yadayada
    yadayada Jun 26, 2009

    ALSO TEST THE IGNITION SWITCH FOR CONTROL POWER.

  • yadayada
    yadayada Jun 26, 2009

    there are more than one hot wire to the controller.

  • yadayada
    yadayada Jun 27, 2009

    we experts work from home we have no access to wiring diagrams, to get a full diagram of the sytem you will need to either use alldata.com or purchase a used factory manual on ebay. generally speaking GM cars and trucks use orange and red for power wire colors with varing color strips on the wire.

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