Heater control problems
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RWD 19xx-1984 DeVille and Fleetwood,
1985-1996 Fleetwood and Brougham Forum Discussion, Heater control problems in Past Cadillac Vehicle Discussion; Hello I own a 1987 Cadillac Brougham 4 door with the 5 liter engine. My car is equipped with the ...
  1. #1
    zachm1 is offline Cadillac Owners Member
    Automobile(s): 1987 Cadillac Broughm
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    Heater control problems

    Hello
    I own a 1987 Cadillac Brougham 4 door with the 5 liter engine. My car is equipped with the electronic climate control. My problem is as follows. When I start the car and let it warm up, the heater will not turn on automatically as it should. However, the defrost position works fine. If I push the defrost button and then any of the auto settings (low, med, or hi) or the econo switch it will work fine. The heater will not come on by itself. I have to put in the defrost mode first. Any help would be appreciated. I thank you in advance.
    Zach

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  3. #2
    MoistCabbage's Avatar
    MoistCabbage is offline Cadillac Owners 10000+ Posts
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    Does it come on by itself once the engine warms up?

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    zachm1 is offline Cadillac Owners Member
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    Re: Heater control problems

    Hello
    No, the heater does not come on when the engine heats up. It can be at full operating temperature and the heater will not turn on by itself. I have to turn on the defrost button first and then any of the auto or econo settings.

  5. #4
    carnut is offline Cadillac Owners Master
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    Re: Heater control problems

    By stating the "heater" wont turn on, you really mean the fan wont turn on in any position except defrost, I would suspect the power module under hood in the heater box up top. Defrost by passes all the automatic fan speeds and in car temp sensors. My second educated guess would be the control head where the buttons are.

  6. #5
    jamespowers is offline Cadillac Owners Enthusiast
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    Re: Heater control problems

    Quote Originally Posted by carnut View Post
    By stating the "heater" wont turn on, you really mean the fan wont turn on in any position except defrost, I would suspect the power module under hood in the heater box up top. Defrost by passes all the automatic fan speeds and in car temp sensors. My second educated guess would be the control head where the buttons are.
    Hmmmm.....I have the same problem in my Brougham. How easy is this to replace?

  7. #6
    cadillac kevin's Avatar
    cadillac kevin is online now Cadillac Owners Master
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    Actually, I believe they are made like this (I'll have to check my FSM).....until the air gets to the desired heat temp on the screen, it will not come out the floor. It will come out the defrost vents, but thats it, until it warms up.

  8. #7
    drmenard is offline Cadillac Owners Enthusiast
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    Re: Heater control problems

    you have a bad temp switch... not sure where it is on that motor.. I know on the earlier years it was on the right side cylinder head, near the first spark plug . but on the 307 not sure where it is...

  9. #8
    cadillac kevin's Avatar
    cadillac kevin is online now Cadillac Owners Master
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    I missed his second post about it doing it even when warmed up....I second the temp sensor.

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    Quote Originally Posted by drmenard View Post
    you have a bad temp switch... not sure where it is on that motor.. I know on the earlier years it was on the right side cylinder head, near the first spark plug . but on the 307 not sure where it is...
    I'm reading through my '86 FSM, and I'm not seeing anything about an engine temp sensor. There is a coolant temp sensor though in the heater water valve.
    According to the FSM "It closes above approx. 95 degrees F and turns on the heater blower. When coolant temp. is below 95 degrees, the switch opens and the programmer will hold the heater blower off until the coolant temp exceeds 95 degrees."

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