Please help--A/C starting by itself
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1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, Please help--A/C starting by itself in Past Cadillac Vehicle Discussion; Hello everybody, After I've changed the A/C a few months ago I'm experiencing a new thing. In the last week ...
  1. #1
    Bogdan's Avatar
    Bogdan is offline Cadillac Owners Member
    Automobile(s): 1995 Deville Concours 4.6 - 140,000 miles
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    Please help--A/C starting by itself

    Hello everybody,
    After I've changed the A/C a few months ago I'm experiencing a new thing.
    In the last week happened already a few times and this is when I'm starting the engine the A/C starts in AUTO mode by itself without touching any buttons.
    What can that be? And if expensive?
    Cadillac Deville Concours 95

    Much appreciated.

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  3. #2
    bigm57ict's Avatar
    bigm57ict is offline Cadillac Owners Connoisseur
    Automobile(s): 1995 Sedan DeVille, 1979 Coupe deVille
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    Re: Please help--A/C starting by itself

    This is a long shot, but all I can think of.
    Since it's getting cooler in the evenings and mornings, are you running the defroster or defogger? I've notice whenever I do, when it is done running, the system defaults back to "auto" even though I had it on "econ" before.

  4. #3
    Bogdan's Avatar
    Bogdan is offline Cadillac Owners Member
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    Re: Please help--A/C starting by itself

    Quote Originally Posted by bigm57ict View Post
    This is a long shot, but all I can think of.
    Since it's getting cooler in the evenings and mornings, are you running the defroster or defogger? I've notice whenever I do, when it is done running, the system defaults back to "auto" even though I had it on "econ" before.
    Well no. I'm not running anything yet and there aro no ON activities (buttons) when I'm shutting the engine. Happened a few times as I started the engine the A/C starts running in AUTO 60 degrees mode by itself.
    Also but not yet 100% sure I think a reset of the gas mileage and total gas consumed messages happens as well.
    I don't know if can maybe something related to A/C vacuum as sometimes is changing by itself from blowing from the frontal ducts to the windshield ones and after seconds comes back and blows again as normal from the front ones and I'm not touching anything and there are no other buttons lit.

  5. #4
    maeng9981's Avatar
    maeng9981 is offline Cadillac Owners Connoisseur
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    Re: Please help--A/C starting by itself

    I guess you're turning the HVAC off with OFF button when you turn off your car? If you are, then it shouldn't come back on automatically unless the battery is too weak and is resetting the IPC every time you start the car. Is the trip odometer resetting to 0.0 ?

    EDIT: Just saw your latest post. Sounds like the battery is going, unless you have IPC issues. What voltage are you getting with the key ON, after the engine off and cooled down for at least 30 minutes? Is your gas door and/or trunk popping open by any chance? Speakers making popping noise?

    Your "changing vent randomly" problems is most likely the system losing vacuum somewhere. It's usually at the parking brake release diaphragm-

  6. #5
    Bogdan's Avatar
    Bogdan is offline Cadillac Owners Member
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    Re: Please help--A/C starting by itself

    Thanks maeng.
    I'll look for the trip reset. Engine started ok lately so I'll keep an eye on it.
    I've changed battery 2 months ago and seems to me that is nothing wrong with it as giving a strong start. I'll check the connections at the battery. Also I'll check to see if any codes are in.

    For the "changing vent randomly" problems the parking brake works ok. Is there a diagram/picture so I can know where are the vacuum lines cabin and under hood also the actuators located?
    Thanks a lot.

  7. #6
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Please help--A/C starting by itself

    There is one or two more lines to the engine I think. Check the under hood portion (lower right view).

    http://parts.nalleygmc.com/showAssem...rimLevel=14342

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