AC Clutch not engaging
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Cadillac Seville / Cadillac Eldorado Forum Discussion, AC Clutch not engaging in Past Cadillac Vehicle Discussion; Finally got around to replacing HVAC blower, and now compressor clutch wont engage. Verified all fuses are good, and inspected ...
  1. #1
    bigo93bronco is offline Cadillac Owners Member
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    AC Clutch not engaging

    Finally got around to replacing HVAC blower, and now compressor clutch wont engage.

    Verified all fuses are good, and inspected and cleaned connections at compressor. When I inspected the relay under the hood, I was able to verify the circuits going to the compressor clutch by removing the relay and using a jumper to short the constant (thick orange) over to the clutch (it engages fine). The problem is that I don't have battery voltage on either of the relay's coil pins with the key in any position (or engine running).

    Its my understanding that 12VDC+ is always supplied to one of the coil pins with the key on, and that the relay engages when the PCM see's that everything is good and sends a ground to the other coil pin to command the clutch on. I also read that this 12VDC+ is supplied from the Cruise control fuse, and must run in series through all the pressure switches before arriving at the relay cavity. There are 3 different sensors on the coolant lines. A large one near the dryer, and 2 smaller ones in the line running a cross the top of the firewall. The large one shows +12VDC on the pink wire and nothing on the other, the small one closest to it shows almost 2 volts on one wire, and the one closest to the brake booster shows a little over +4VDC on one wire. Can someone put me on the right track here?

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  3. #2
    basscatt's Avatar
    basscatt is offline Cadillac Owners Master
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    Re: AC Clutch Not engaging

    Quote Originally Posted by bigo93bronco View Post
    Finally got around to replacing HVAC blower, and now compressor clutch wont engage.

    Verified all fuses are good, and inspected and cleaned connections at compressor. When I inspected the relay under the hood, I was able to verify the circuits going to the compressor clutch by removing the relay and using a jumper to short the constant (thick orange) over to the clutch (it engages fine). The problem is that I don't have battery voltage on either of the relay's coil pins with the key in any position (or engine running).

    Its my understanding that 12VDC+ is always supplied to one of the coil pins with the key on, and that the relay engages when the PCM see's that everything is good and sends a ground to the other coil pin to command the clutch on. I also read that this 12VDC+ is supplied from the Cruise control fuse, and must run in series through all the pressure switches before arriving at the relay cavity. There are 3 different sensors on the coolant lines. A large one near the dryer, and 2 smaller ones in the line running a cross the top of the firewall. The large one shows +12VDC on the pink wire and nothing on the other, the small one closest to it shows almost 2 volts on one wire, and the one closest to the brake booster shows a little over +4VDC on one wire. Can someone put me on the right track here?
    ------------------------
    AC problems are USUALLY pressure-related -

    to diagnose AC problems -
    you need to connect a quality set of guages -

    then post BOTH the HIGH pressure readings -
    and the LOW pressure readings -

    along with the ambient - outside - air temp -

    and the air discharge temp at the center AC vent -
    with the temp set at 60* and a medium speed fan -

  4. #3
    bigo93bronco is offline Cadillac Owners Member
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    Re: AC Clutch Not engaging

    I don't have gauges or equipment to do that kind of stuff. I'm perfectly willing to take it to an AC shop, I just want to rule out basic wiring issues first. After doing more reading I found the high pressure switch at the front of the car, and there is no voltage on either wire there. I am assuming that is because the low pressure switch near the firewall is not passing that voltage along (indicating either a bad sensor, or Freon level low). The low pressure switch shows +12V on one wire and nothing on the other. If I can establish that either the low pressure sensor is faulty or that the Freon is actual low, i'll just take it to get it serviced.

  5. #4
    basscatt's Avatar
    basscatt is offline Cadillac Owners Master
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    Re: AC Clutch Not engaging

    Quote Originally Posted by bigo93bronco View Post
    I don't have gauges or equipment to do that kind of stuff. I'm perfectly willing to take it to an AC shop, I just want to rule out basic wiring issues first. After doing more reading I found the high pressure switch at the front of the car, and there is no voltage on either wire there. I am assuming that is because the low pressure switch near the firewall is not passing that voltage along (indicating either a bad sensor, or Freon level low). The low pressure switch shows +12V on one wire and nothing on the other. If I can establish that either the low pressure sensor is faulty or that the Freon is actual low, i'll just take it to get it serviced.
    ----------------------------------
    have you checked for fault codes?

    system failures - and defective monitored electrical componants -
    will usually set a code -
    -----------------------------------

    the problem is you are trying to diagnose the issue backwards -

    in 30+ years of working on AC systems -
    I have never started with probing electrical components -

    PRESSURE is the heart of the system -

    and FIRST step is ALWAYS connecting gauges - and checking pressures -

    sorry - I can't help any more than that -

  6. #5
    bigo93bronco is offline Cadillac Owners Member
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    Re: AC Clutch Not engaging

    The only codes I have are suspension codes. The reason I started troubleshooting that way, is because the compressor has always worked fine, we just haven't used it in a few months (or the car for that matter) since the blower went out. Kinda sounds like we may have lost refrigerant while it was sitting, so not having the equipment to check it myself I guess i'll take it to the AC guy in town

  7. #6
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: AC Clutch Not engaging

    If it lost refrigerant, there should be a low refrigerant code

  8. #7
    bigo93bronco is offline Cadillac Owners Member
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    Re: AC Clutch Not engaging

    I might have to drive it a bit more to see if anything like that eventually pops up. I have no P codes whatsoever right now. Could switching out the factory radio to an aftermarket unit have anything whatsoever to do with this? I only ask this because I recall reading something in another thread that mentioned something about a data stream from the CCC to the radio, and making sure the clock came up or something.

  9. #8
    Ranger's Avatar
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    Re: AC Clutch Not engaging

    Low refrigerant (as well as all HVAC related failures) will be a B (Body) code.

  10. #9
    basscatt's Avatar
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    Re: AC Clutch Not engaging

    Quote Originally Posted by Ranger View Post
    Low refrigerant (as well as all HVAC related failures) will be a B (Body) code.
    ------------------------------------------------
    1994 Eldo would be OBD1 codes - so there could be "A" codes -

  11. #10
    bigo93bronco is offline Cadillac Owners Member
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    Re: AC Clutch Not engaging

    got I045 (always had that one) A011, and A012 (never had any A codes before, and these remained even after clearing codes, and not starting the engine)

  12. #11
    basscatt's Avatar
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    Re: AC Clutch Not engaging

    Quote Originally Posted by bigo93bronco View Post
    got I045 (always had that one) A011, and A012 (never had any A codes before, and these remained even after clearing codes, and not starting the engine)
    ---------------------
    got I045
    there is no I045 that I can find -
    the closest is a T045 - LF ABS Valve Solenoid Fault -
    or P045 (E045) - Right Oxygen Sensor Signal Rich -

    A011 - High Side Temperature Sensor Circuit

    A012 - Low Side Temperature Sensor Circuit

  13. #12
    bigo93bronco is offline Cadillac Owners Member
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    Re: AC Clutch Not engaging

    what does the 11 and 12 tell me?

  14. #13
    basscatt's Avatar
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    Re: AC Clutch Not engaging

    Quote Originally Posted by bigo93bronco View Post
    what does the 11 and 12 tell me?
    ----------------------------
    those codes mean the freon temperature sensors
    are not delivering the information to the AC programmer -

    either the sensors are defective - or unplugged -

    or the wiring to the sensors is bad -

  15. #14
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    Re: AC Clutch Not engaging

    Quote Originally Posted by basscatt View Post
    ------------------------------------------------
    1994 Eldo would be OBD1 codes - so there could be "A" codes -
    Oops! I was obviously in OBDII mode. Thanks for the correction.
    basscatt likes this.

  16. #15
    Ray Slay is offline Cadillac Owners Member
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    Re: AC Clutch Not engaging

    The PCM will shut down the compressor clutch when low refrigerant is detected. Not saying you have that problem. If so you will have to unhook the battery ground cable and reboot before the compressor clutch will again engage. My personal experience on this one. Only at that time will you be able to recharge the system.

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