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Thread: Heater/AC fan will not turn off.

  1. #1
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    Heater/AC fan will not turn off.

    Hi All, when the car is on the fan will not turn off, I am assuming that this is the fan switch since it will not change speeds and will not allow me to turn it off. If there is anything else that could cause this please let me know.


    Andy

  2. #2
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    Quote Originally Posted by south42 View Post
    Hi All, when the car is on the fan will not turn off, I am assuming that this is the fan switch since it will not change speeds and will not allow me to turn it off. If there is anything else that could cause this please let me know.

    Andy
    Heater blower motor resistor, usually it manifests itself in other ways but I would highly caution you driving the car with this issue. There have been plenty of e34's burned up from these.

    I'm off to bed but use the search and read up, I'd hate to see another one burn. Dinandave just shorted his 535/5 from a similar issue I believe. If you smell smoke its probably already to late.

    Pull blower motor fuse and keep a fire extinguisher handy if you must drive before you can fix it.

    Good luck.

    Or it just might need a new hvac unit
    Last edited by kingp1n; 06-27-2013 at 02:47 AM.

  3. #3
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    11/88 E32 750iL+98 E36M3
    in case you mean the blower motor for heating and your car has a heater sword: remove the sword from right side / passenger side legroom, remove the plastic cap on the handle of the sword and underneath you find a relay. This is always stuck closed, re-bend the contacts a bit and it will work again.
    http://www.bimmerboard.com/members/s...word_relay.jpg

    the SWORD has a 5 pin connector

    Pin 1 connector for the potentiometer for speed regulation at the control panel.
    Pin 2 power supply
    Pin 3: the relay get's contact when the blower fan potentiometer is adjusted, 12 volts come on.
    Pin 4 is ground
    Pin 5 the cable/wire from the blower fan.
    Remove the plastic covers from the sword and connect it again to the control panel.
    Use a multimeter to test it.
    When you turn the thumbwheel at the potentiometer, the voltage at pin 1 changes from 1.1 - 4.25 volts. As the transistor, which amplifies the potentiometer, only has a voltage (input) of 5 volts, that should be the full power of adjustment.


    In case the fan speed cannot be changed, then the sword needs to be repaired
    http://www.bimmerboard.com/forums/posts/355700/

    In case your car has a resistor instead of a sword, replace the resistor
    http://www.bmwe34.net/E34main/Mainte...ical/Sword.htm
    Shogun tricks and tips for the E32 series are HERE!

  4. #4
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    OK, took the sword out and adjusted the contacts and did not change anything. I was able to adjust the speed of the fan buy pushing the contacts closer. Starting to think it is the switch that is stuck on. Does anyone know when the hvac was changed? I have one from a 92 and it is different from my 89. The plugs and switches are different on the back of it.


    Andy

  5. #5
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    OK, does anyone disagree with my thoughts?


    Andy

  6. #6
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    No, sounds like solid theory to me. First thing I thought when I read your post was maybe it is the switch.

    Can't say I have too much experience with this other than my sword is starting to go bad - it blows erratically sometimes. Blowing erratically or having either 'off' or 'full blast' are the failure modes I have heard of. I have never head of not being able to turn it off at all.

    The Bentley lists the HVAC systems below. IHKR I and IHKA have the final stage 'sword'. IHKR II and III have the series resistors.






    - - - Updated - - -

    e34HVAC.jpg

  7. #7
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    OK so I replaced the whole hvac panel, (what a pain in the ass for an early car since it was only used until 01/1990) and that did not fix the problem. So I replaced the sword, but now it only works on high. I can turn it off but only high works? I believe that this a sign of a sword going bad, are there any other parts to replace?

    Andy

  8. #8
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    Previous sword was totally bad. Current sword only has bad transistors, which are relatively easy to replace.
    demet

  9. #9
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    Quote Originally Posted by demetk View Post
    Previous sword was totally bad. Current sword only has bad transistors, which are relatively easy to replace.

    Ya but I am not good with electrics, and I do not know how to soldier.


    Andy

  10. #10
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    Send it to me and I'll fix it for ya.
    demet

  11. #11
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    My blower runs at a low speed when the control is set to 0 and key in position II.

    I always thought this was normal. I will see about the relay on my sword.

    Quote Originally Posted by 1990525i View Post
    the bees knees

  12. #12
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    With the problem with the sword should I run the fan?


    Andy

  13. #13
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    Quote Originally Posted by south42 View Post
    With the problem with the sword should I run the fan?


    Andy
    Absolutely not! And I am being very serious.
    demet

  14. #14
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    Well after many tries I finally got a good sword and on what looks like the last day of heat I have a working fan and AC. So this at least means I also now have heat.


    Andy

  15. #15
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    New findings on this problem:
    German, below English:
    Ergaenzung: Heizschwert- Geblaese geht nicht aus. Nach dem hier nun oefters die Frage gestellt wurde, warum das Geblaese nicht ausgeht, obwohl der Schalter auf "0" steht, hier nun des Raetsels Loesung: Es ist der Leistungs-FET. Er ist durchgeschlagen, d. h. hat einen Kurzschluss. Test: In der Stellung "MAX" laeuft das Geblaese geringfuegig schneller als in dem Regelbereich. Das liegt an dem Relais, welches bei "MAX" die FETs brueckt. Um den defekten FET zu finden, muessen alle FETs ausgeloetet werden und wie in dem Anhang gezeigt, getestet werden. Mit zwei Fingern abwechselnd 1 und 2 (AN) und 1 und 3 (AUS) beruehrt werden. Es handelt sich um BUZ71, BUZ11 kann ebenso verwendet werden. Also auch diese Fehlervariante kann am Heizschwert auftreten.

    Link with pic how to test: http://www.7-forum.com/forum/showthread.html?t=111467

    English: Additional info: Heater sword does not stop the blower fan.....This question was aked before several times, why the blower does not stop, although the switch is on "0", here now the solution:

    It is a defective Power MOSFET . It has a short circuit.
    Test: In the "MAX" position, the fan runs slightly faster than in the control range. This is due to the relay, which bridges the FETs at "MAX". To find the faulty FET, all FETs must be de-soldered and tested as shown in the appendix. With two fingers alternately 1 and 2 (ON) and 1 and 3 (OFF) are touched. It is BUZ71, BUZ11 can also be used. So this error variant can occur on the heater sword too.
    Shogun tricks and tips for the E32 series are HERE!

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