A/C clutch always engaged

Discussion in 'Kenworth Forum' started by jjtrucking, Sep 22, 2012.

  1. jjtrucking

    jjtrucking Bobtail Member

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    When you plug the A/c clutch in it always turns on with the system empty of freon
     
  2. chalupa

    chalupa Road Train Member

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    A switch like h/p or l/p is bad. Something is telling comp to run. Unplug comp and use test light. Freon and comp both have oil that is now missing.

    Bottom line is you have to find signal to comp. Start with pressure switches then move to sleeper ( has sleeper right? ) . Check everything , be looking for discolored wires ( shorts) burn connections etc.

    Good hunting
     
  3. bender

    bender Road Train Member

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    What truck? Is the dash control off when this occurs?
     
  4. jjtrucking

    jjtrucking Bobtail Member

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    It's on a 97 w900 is the low and high pressure switch suppose to be both on the high pressure line
     
  5. chalupa

    chalupa Road Train Member

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    No... lp switch on big line or drier, hp switch will be on little line if it has one. FYI on newer KW nothing works in a/c without air. Kw figures w.o air then clutch fan can't engage and system will over pressure.

    Unplug both switches and see if test light lights up at comp. ( member I said dont run it w/o freon ) be a quick way to eliminate these guys. Also make sure dash control is not on defrost, that will call for comp to dehumidify but that's another issue.

    Test those switches one at a time and see what you have.
     
  6. jjtrucking

    jjtrucking Bobtail Member

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    on this truck it has the high and low pressure switch side by side on the high pressure side it looks to me it came from the factory like this I looked on the dryer and there is no place to put the switch
     
  7. truckmechanic

    truckmechanic Medium Load Member

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    Check the compressor relay