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Thread: AC clutch not engaging when bypassing relay

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    Default AC clutch not engaging when bypassing relay

    My AC stopped working last summer but I never got around to fixing it. I now am troubleshooting it and noticed that if I try to bypass the AC relay by supplying 12 volts to the AC clutch from the fuse box, middle P/Y terminal of relay, the clutch does not engage. That would mean a broken wire somewhere as the current can't get to the clutch? Does anyone know where that wiring harness is routed? I will try 12 volts straight at the AC compressor to see if it engages the clutch.

    Car is a 2005 Mazda 3 GT hatchback.

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    Uncle Ben
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    Default Re: AC clutch not engaging when bypassing relay

    Either broken wire or the compressor (clutch electronics) are no good.
    Access the compressor and check continuity with the volt meter of the cars side wiring to the relay. If that's good then you know ots the compressor
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    Default Re: AC clutch not engaging when bypassing relay

    The AC compressor will not kick on if your refrigerant is too low; there is a pressure transducer in line with the electrical circuit. Check your refrigerant level too

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    Default Re: AC clutch not engaging when bypassing relay

    Quote Originally Posted by morganc View Post
    The AC compressor will not kick on if your refrigerant is too low; there is a pressure transducer in line with the electrical circuit. Check your refrigerant level too
    Forgot about that, good point.
    OP does state he is trying to bypass the relay and it's not clicking. If he is bypassing it, it should click regardless

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    Default Re: AC clutch not engaging when bypassing relay

    Depends where the transducer is in the system; if it's after the relay then bypassing the relay still won't make a difference. OP, try jumping a 12v dummy wire right to the compressor terminal then work backwards from there.

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    Default Re: AC clutch not engaging when bypassing relay

    I looked up the diagram on all data. Can't post at the moment. On my phone
    Relay
    Pin 30 power from battery
    Pin 87 power going straight to the compressor magnetic clutch. Clutch is already grounded on other end
    Pin 86 power from switched ignition source
    Pin 85 ground from ecu. This will turn on the relay

    The switch you are referring to feeds to the ECU



    Last edited by McGuyver_3; Yesterday at 07:31 PM.

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