'90 DeVille - A/C too cold (stuck on high)
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, '90 DeVille - A/C too cold (stuck on high) in Past Cadillac Vehicle Discussion; The blower control works fine. In AUTO mode, however, the compressor stays on. In a few minutes it gets very ...
  1. #1
    Notaguru is offline Cadillac Owners Fanatic
    Automobile(s): 1990 DeVille
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    '90 DeVille - A/C too cold (stuck on high)

    The blower control works fine.

    In AUTO mode, however, the compressor stays on. In a few minutes it gets very cold and must be switched to ECON for a while.

    Where is that thermostat, and can it be serviced? If not, where do I get a working one?

    Or could it be a stuck relay? If so, where is it?

    Thanks

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    Ranger's Avatar
    Ranger is online now Cadillac Owners Member
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    Re: '90 DeVille - A/C too cold (stuck on high)

    Start by pulling the DTC's.

    The "thermostat" would be the in car temperature sensor or aspirator. It is located behind a 1" square grill somewhere on the dash. It may or may not be the problem.

  4. #3
    Notaguru is offline Cadillac Owners Fanatic
    Automobile(s): 1990 DeVille
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    Re: '90 DeVille - A/C too cold (stuck on high)

    THANKS

    There are no stored codes.
    I now have a service manual, but the climate control information is scattered in several locations. I had hoped that this was a common problem.

    The circuit cannot be too complicated: a sensor, and a controller that includes a means for comparing sensor data to controller input, and a relay that applies power to the compressor clutch.

    But the relay can't be stuck because the compressor clutch is not engaged when the system is in ECON mode. So it should be the sensor or the controller (that module in the dash). Does that make sense?

    I'll keep searching in the manual...

  5. #4
    Ranger's Avatar
    Ranger is online now Cadillac Owners Member
    Automobile(s): White Diamond '03 DHS (with DTS floor shift)
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    Re: '90 DeVille - A/C too cold (stuck on high)

    The sensor would be the more likely culprit in my estimation.

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