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  • Engaging compressor clutch

    Experts needed: My car is a 2004 Cavalier. I've replaced the compressor (reman), oriface, high/low pressure sensor and receiver/drier along with throughly cleaning the rest of the system.

    I've tested all the wiring from the pressure sensor to pcm, compressor to relay, relay to fuse, fuse to batt, relay to pcm, pcm to ground, pcm to bcm.

    There is a resistor in the wiring for the compressor. It connects the power side to ground that I couldn't read any resistence from so I've tried 2 used ones as well. Never got any readings from the 3 but I believe that's more of me not knowing what setting to use on my DVOM instead of faulty resistors. From what I've learned, that resistor is only there to absorb some of the energy during disengagement from damaging the pcm & coil.

    Also, my compressor coil shows 4 ohms when checked.

    My static pressure is about 80 once both sides has equaled out.

    The compressor will engage if I jump the relay so I believe my issue is being caused by the pcm somehow.

    Is there anything else I can do before giving up and paying a shop?

    I do have some software and a bluetooth elm device but the only thing I have been able to find there is that the pcm reports "AC refrigerant: not available/completed."

    Also, I've tried swapping over to a different computer/bcm with no luck there as well.

    It doesn't display my AIT sensor right either so I'm thinking the 2 are related somehow because I have a good reference signal to it and I checked for continuity between the sensor and pcm but it still doesn't work.

    Other than the AC and AIT sensor, the car doesnt have any other issues.

    Sorry it's so long, just wanted to be detailed and thanks in advance.

  • #2
    Careful jumping anything. Some may have if OE stickers in place to reset once it was low quit allowing compressor. You have at least enough static pressure but needs to be reset via your device or usually disconnect neg bat, allow some time but AYOR you lose info for other control modules memory. Idle may be lousy for a while.

    Coil OHM are OK. If when you jumped it high side spiked it would trigger a shut down.

    Other is AYOR with reman parts. Condenser is almost a must if compressor burned out can't clean anything it all gets tossed for new - worse is each time if this is burning up again stinks,



    Tom
    MetroWest, Boston

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    • #3
      Well, I haven't jumped it and let it run. Only long enough to hear clutch engage. Basically making sure that circuit was good as well as the coil.

      As far as the pcm reset: I've had the batt disconnected multiple times during all this, resetting the PCM doesn't scare me. That hasn't affected the situation at all.

      As far as the condenser being clean, I put a gallon of some alcohol based stuff I can get through work through most of the parts. They're definitely clean. After that product started coming out clean, I used a 110 psi airline that's connected to 3 industrial sized compressors. Probably 1000+ gallons of capacity total. (I work for the biggest tire retailer in the U.S.) Trust me, the lines, condenser, and evaporator definitely got cleaned. Everything else is new.

      I'm just at a loss here about what else could be preventing the system from functioning. I'm sure I've checked every circuit for continuity & proper voltage.

      I'm almost ready to put together an entire test bench type setup while using either air pressure to engage the high/lo sensor or run a really long extension out to mine on the car from the garage. I have enough extra pieces at the moment that I should be able to make functional. (PCM, BCM, high/lo thermistor, compressor with coil, all the engine wiring including pcm connectors, bcm connectors, and OBD2 port.... desktop power supply...)

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