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  1. #1

    Default 99 Sub rewire a/c activation switch

    Anyone have any experience with putting in an external switch to run power to engage the clutch. My panel is acting up the a/c button when depressed does nothing. I get cold air and the compressor clutch engages when on defrost only. Was wondering if anyone knew which wire running to the back of the control panel powers the clutch so I can put in an ignition powered toggle switch. I dont want to run a seperate wire from the compressor.
    Saint Petersburg FL
    1999 SUBURBAN LT C1500
    1987 BMW 325IS
    1994 Infinti Q45
    1997 Nissan Maxima GLE

  2. #2
    Legend unplugged's Avatar
    Join Date
    Sep 2006
    High Deserts of SoCal


    A friend of mine has a Volvo with a custom toggle switch on the dash for the ac. He didn't wire it through the ignition circuit so every now and then he forgets to turn it off and returns to find a dead battery.

    That said, you should probably interrupt the circuit at the relay that controls the compressor. It's in that pod of fuses and relays under the hood. find which pin controls the compressor and either cut or pull the wire loose below the pod and splice the wires for your switch in there.
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  3. #3


    I would find out why the a/c clutch isn't engaging with the a/c switch on. It's got to be that some other condition is causing it to not engage, like the pressure switch on the accumulator or something.

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  4. #4


    The clutch engages when the control knob is switched to any of the defrost settings and the air is cold but it is not directed out of the front vents which makes it inefficient. I'm assuming that if the clutch engages on defrost and the air is cold the pressure switch is not the cause of the problem.

    When the A/C button is depressed regardless of whether it is on defrost or not the clutch disengages. The light on the A/C button does not illuminate as it had been before.

    Thanks for the tip on the relay point.

  5. #5
    Legend unplugged's Avatar
    Join Date
    Sep 2006
    High Deserts of SoCal


    Adapt and improvise. It's the American way.
    It's just a simple bypass switch. It's not a complete re-work of the ac.

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