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Thread: Blower switch in dash or blower resistor?

  1. #1
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    Blower switch in dash or blower resistor?

    Hi all,

    I've had issues with the operation of the blower resistor before (always running at full speed) and have been able to clean it up to get it working correctly. The current issue is a little different though. All speeds work fine (1,2,3,4). It is just that 0 runs like 1. (the fan won't shut off, unless the key is turned to off in the ignition)

    Is this something that the blower resistor could cause? I'm thinking it might be the switch in the dash itself (which seems clicks into place nicely as it should and always has) that would cause the problem this time. I'm not sure of the wiring to the resistor, but was thinking that it shouldn't get power at all on 0.

    Wondering if anyone can share their experiences if they've had the same problem.

    Edit - just checking the wiring diagram (posted), It does seem like it is the switch if I'm reading it right. 0 shouldn't connect at all. Do any electrical engineers disagree?Screen Shot 2019-01-12 at 12.08.29 pm.png
    Last edited by mobilenet; 01-11-2019 at 08:12 PM.

  2. #2
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    Yes, I disagree. So does the diagram you posted. Look at the two feeds labeled A and B, all connected to the low speed circuit.


    /.randy

  3. #3
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    Thanks Randy.

    You are correct. They I think come from the AC and Recirculation circuits? It turns out I had recirc on, which is why the 1 speed was blowing even with the fan dial set to 0.

  4. #4
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    The blower runs at the lowest (or higher when selected) speed ANY time the a/c circuit is energized. Otherwise, the evaporator coil would be contained in a block of ice, inhibiting airflow.
    Last edited by Randy Forbes; 01-12-2019 at 07:25 AM.

  5. #5
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    That makes sense. Seems that just the recirc even with ac off triggers the fan to run for me. Not sure if that is normal or necessary but it’s simple enough to turn it off. I guess it is designed to keep the recirculated air recirculating.

  6. #6
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    Exactly. Low speed enabled any time the switch is set to 1, the A/C is on, or the outside air door is closed. They want to keep a bit of air moving through the heater box. My guess is they are trying to avoid that old Ford musty smell.


    /.randy

  7. #7
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    Quote Originally Posted by mobilenet View Post
    ... It turns out I had recirc on, which is why the 1 speed was blowing even with the fan dial set to 0.
    This function is mentioned in the Owners Manual without explanation of what causes the recirculation after outside air is blocked.
    Recirculated air mode
    If there are unpleasant odors in
    the outside air, you can temporarily
    block the flow of air. The
    system then recirculates the air currently
    within the vehicle.
    BMW MOA 696, BMW CCA 1405

  8. #8
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    Thanks to both of you for the help. :-)

  9. #9
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    Have the same issue but slightly different. I just changed the blower resistor. Prior to it not working, my fan speed at 0 and 1 are also the same.

    After an hour drive, it noticed some whining then when I changed the blower speed to 3, that's when it stopped working (Except for #4 blower)

    With the new resistor installed, things seem back to normal but it's still blowing at 0 and 1 and I can still hear the whine.

    Does this mean my blower motor is about to be done?

    Why is the blower fan still running at 0? So is the blower fan always running normal? Yes I have the circulation on to prevent outside air because these z3's don't have no cabin filter. (just got the car 3 months ago) Thanks
    Last edited by RayBallen; 10-06-2019 at 07:16 PM.

  10. #10
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    0 & 1 are the same when the a/c is switched on, or the evaporator coil would freeze over.

  11. #11
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    Quote Originally Posted by Randy Forbes View Post
    0 & 1 are the same when the a/c is switched on, or the evaporator coil would freeze over.
    I see. Same thing with recirculation on to prevent outside air as Vintage stated? Double checking.

    The issue now I have is the whining. I'm not sure if it's been there before. Maybe it's just me.
    Last edited by RayBallen; 10-06-2019 at 07:35 PM.

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