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Thread: heating and a/c system please help

  1. #1
    yungwun724 is offline Cadillac Owners Member
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    heating and a/c system please help

    ok i live in md and right now its about 45 degrees outside but my outside temperature reads 85 degrees on my car...and i notice when i set my heat on 90 degrees it gets real hot then when i turn it down 2 85 cold air blows from the vents at first cold air didnt start coming out until 75 degrees..can someone tell me wat the problem is?


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  3. #2
    JimD is offline Cadillac Owners Connoisseur
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    Re: heating and a/c system please help

    What year-model of car?

    You should replace the outside ambient air temperature sensor because some year-model Cadillacs use that information as an input to the HVAC system.

  4. #3
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: heating and a/c system please help

    Yup, your car thinks it is 85 degrees, so when you ask for 75, it thinks it has to cool to reach that temperature.

  5. #4
    krimson_cardnal's Avatar
    krimson_cardnal is offline Cadillac Owners Enthusiast
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    Re: heating and a/c system please help

    So how does this happen? With defective out side air temp sensor it defaults to the inside air? Which years, very strange behavior, never heard of it... K_C

  6. #5
    yungwun724 is offline Cadillac Owners Member
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    Re: heating and a/c system please help

    it iz a 97 deville

  7. #6
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: heating and a/c system please help

    I believe that the OAT sensor is also linked to the HVAC system. If it is 20 degrees outside and the car thinks it is 95, it is going to cool to reach a requested 75 rather than heat to do it.

  8. #7
    yungwun724 is offline Cadillac Owners Member
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    Re: heating and a/c system please help

    where is my outside temperature thermonitor located at

  9. #8
    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: heating and a/c system please help

    It's the small black item at the end of a covered wire clipped to the front of the hood latch/radiator support. Single plug with safety catch. New unit is about $14 at www.rockauto.com. BTW, it's a thermistor; a resistor which changes value as temperature varies.


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