ac/heat doesn't turn off and drains battery, which fuse?

Discussion in 'General Motoring' started by osote, Jun 17, 2004.

  1. osote

    osote Guest

    OK, I noticed that the ac/heat doesn't turn off and that is what is
    causing the battery drain that makes my battery run down every night
    unless I pull the fusible link before I go to bed and hook it back up
    in the morning before I drive it.

    What fuse goes to the ac/heat on a 91 subaru legacy wagon and is it in
    the main box inside or in the engine compartment?
     
    osote, Jun 17, 2004
    #1
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  2. osote

    Edward Hayes Guest

    Owners manual?? or start pulling fuses one by one.
     
    Edward Hayes, Jun 17, 2004
    #2
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  3. osote

    « Paul » Guest

    Do you mean the interior "blower motor"?
    Do you mean "high speed" if you meant "blower motor"?
    If so, most cars have a blower motor relay that sometimes gets it's
    contacts welded closed. On a 91 Subaru... I am not sure.
     
    « Paul », Jun 17, 2004
    #3
  4. osote

    osote Guest

    I don't know for sure what the word is for what I mean. The A/C OFF
    button is pressed in but you can hear the fan going and if you slide
    it from 1 up to 4 it blows harder even when the OFF button is clearly
    pressed in.

    How do the relay contacts get welded closed and how can I fix this?

    I tried pulling the 2 heater fuses and the main fan fuse and the damn
    thing still worked!
     
    osote, Jun 17, 2004
    #4
  5. osote

    osote Guest

    I don't know for sure what the word is for what I mean. The A/C OFF
    button is pressed in but you can hear the fan going and if you slide
    it from 1 up to 4 it blows harder even when the OFF button is clearly
    pressed in.

    How do the relay contacts get welded closed and how can I fix this?

    I tried pulling the 2 heater fuses and the main fan fuse and the damn
    thing still worked!
     
    osote, Jun 17, 2004
    #5
  6. osote

    « Paul » Guest

    Usually there is only one relay and it is for high speed operation.
    Current draw at high speed may too much for a dash switch and so a
    relay is used. HOWEVER... that does not sound like your problem because
    you can change blower speed. Isn't your A/C off button only for the
    compressor and not the blower? Most (all???) cars that have that button
    use it to turn the compressor on and off, only. Could Subaru route ALL
    fan power through the relay? I don't know. Relays sometimes get burned
    contacts due to excessive current draw or wear.
     
    « Paul », Jun 18, 2004
    #6
  7. osote

    JW Guest

    wrote:


    Usually there is only one relay and it is for high speed operation.
    Current draw at high speed may too much for a dash switch and so a
    relay is used. HOWEVER... that does not sound like your problem because
    you can change blower speed. Isn't your A/C off button only for the
    compressor and not the blower? Most (all???) cars that have that button
    use it to turn the compressor on and off, only. Could Subaru route ALL
    fan power through the relay? I don't know. Relays sometimes get burned
    contacts due to excessive current draw or wear.

    Being an electrical engineer, I am astounded by the foolish routings of
    electrical circuitry in the Subaru! I love the car but what is the reason
    the cruise control is routed through one of the horns? Or why is the
    heater motor routed through the other one! I had a gas tank full of rust
    and found out the next years tank Which I found to replace it, although
    all the connections were all identical, blanked the digital dash. I had
    to change the float in the tank to make the dash work again!
     
    JW, Jun 18, 2004
    #7
  8. osote

    CompUser Guest

    And why modulate panel brightness by varying
    resistance *to ground*....weird! 8^B
     
    CompUser, Jun 18, 2004
    #8
  9. osote

    SteveG Guest

    You are not approaching this right, looking for a quick fix rather
    than understanding what you are doing. The blower fan should work
    whether or not the A/C is on. The main fan is the main coolant fan,
    not the heater-A/C blower fan.

    It would be best if you purchased a workshop manual that included
    wiring diagrams, but as was suggested some time back you might be able
    to make some progress without them if you would follow the good advice
    previously given. Place an ammeter between the battery and ground and
    test each circuit individually for a current draw by removing one fuse
    at a time. If you find one that drops the current, that circuit is the
    likely problem. Then you'll have to examine that circuit and the items
    on it, which might or might not be easy without a circuit diagram, but
    at least you'll know at that point whether you'll need one.

    Proceeding methodically is what is needed here.

    Good luck,
    Steve
     
    SteveG, Jun 19, 2004
    #9
  10. osote

    John G Guest


    It would not seem as though an ammeter is really required if he can hear
    the fan running when it should be OFF.
    All he has to do is find the control that is not controlling it and fix
    it.
    Puling the fusible link stops it.
    Then find the actual fuse that stops
    Then find the switch or relay.
    Elementary my dear Watson.
     
    John G, Jun 19, 2004
    #10
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