AC Compressor only engages if you bypass relay.
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This is a discussion on AC Compressor only engages if you bypass relay. within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; My 2002 Subaru AC compressor does not engage unless you bypass the relay. I pulled a full vacuum to -30psi ...

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    AC Compressor only engages if you bypass relay.

    My 2002 Subaru AC compressor does not engage unless you bypass the relay.
    I pulled a full vacuum to -30psi and it sat overnight prior to refilling. It has 18oz of r134, no leaks, relays are good, and blows cold when you bypass the relay. I have replaced the Evaporator core, temp sensor, expansion valve (twice), high side ac hose, the condenser, ac drier, compressor, and all o-rings within the last 5000 miles.

    I have researched this problem extensively, and have completed all the troubleshooting suggestions I could find( replace expansion valve, too much or too little pressure, bypass high low sensor). I made a video and uploaded it here so you can see the issue in detail:
    https://www.youtube.com/watch?v=kfzNSg6uMOg

    The only theory I have right now is that the sensor in the evaporator core which I replaced per the Subaru service bulletin went bad, and that sensor is preventing the compressor from engaging?

    I am tempted to permanently bypass the relay with a toggle switch that will control the fan and compressor, but I am worried that doing that will cause the evaporator to freeze over.

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    Quote Originally Posted by mikechandler82 View Post
    My 2002 Subaru AC compressor does not engage unless you bypass the relay.
    Any solution yet? I have been trying to get the air conditioner work in my bug eye. So far I replaced the busted idle pulley and the belt. I bought a can of freon with the gague but the compressor is not running. Ive been looking for the low pressure switch to jump the compressor but cant find it.

    Can you describe how to bypass the relay?

  4. #3
    Registered User scoobaru03's Avatar
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    If your taking the relay out of the circuit and jumping the pins one would believe that the relay is bad.
    2003 Impreza WRX Sport Wagon

    "I wouldn't want to belong to a club that would have me as a member." - Groucho Marx

    Is it fast? I don't even know if its street legal. O.o (IROC-Z)

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    Quote Originally Posted by dan4451 View Post
    Any solution yet? I have been trying to get the air conditioner work in my bug eye. So far I replaced the busted idle pulley and the belt. I bought a can of freon with the gauge but the compressor is not running. Ive been looking for the low pressure switch to jump the compressor but cant find it.

    Can you describe how to bypass the relay?
    I ended up trading it in for the slower but cooler BRZ. Even Subaru had to to send it out to a specialist since they were stumped... never did find out what was wrong with it.

    To bypass, you can run a wire directly from battery and touch it to where the ac compressor is, but I would recommend also manually powering the fans as well or the pressure will build up and blow your lines. Also monitor the pressure closely. you can kinda get an idea by looking at the wires in the video I posted. Good luck...

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    At that time I swapped known good relays, bypassing was just for troubleshooting.

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