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Thread: E39 almost burned!! AUX FAN ISSUE PLEASE HELP!

  1. #1
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    E39 almost burned!! AUX FAN ISSUE PLEASE HELP!

    Hello All,

    My 2001 E39 525i almost burned yesterday. Came from the aux fan motor as my mechanic has mentioned. I know 2001 models had a recall referenced to this issue. Called dealer and BMWNA and the aux fan has been changed in 2002.

    Question: I know the earlier version aux fans (i.e. 96-97 E39s) have better aux fan motors (SIEMENS). Would I be able to use the pre facelift aux fan/motor/assembly to my 2001 facelift E39 to avoid this kind of situation??

    If not or so, what would be my best replacement for the aux fan assembly to avoid and compromise the safety of my family.

    I would appreciate any thoughts on this. Thank you all for your help!!

  2. #2
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    Siemens motor is for 96-98 only.
    Best is to buy a brand-new BMW aux fan for year/model.

    Then install 2 smoke alarms: one in garage and one inside your house (kitchen), and connect them together.
    The smoke alarm in your garage, use the 120V type sold at hardware store such as Home Depot (but use ONLY 9V battery, no need to hook up to 120V) that allows to hook another smoke alarm inside the house.

    This way if there is smoke in the garage, it will set off BOTH alarms in the garage and your kitchen.

  3. #3
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    There should be a less annoying alternative. I don't believe that we should have to deal with this loud obnoxious fan. I always turn off my AC before coming to a light or any stop, yes I find it that annoying.

  4. #4
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    Actually the Aux Fan in later models 1999+ I6 may turn on by itself or short-circuits by itself causing fire in the middle of the night.

  5. #5
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    Thanks for the inputs guys. No other alternatives?

  6. #6
    JimLev's Avatar
    JimLev is offline Artifically Aspirated Moderator
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    Quote Originally Posted by cnn View Post
    Actually the Aux Fan in later models 1999+ I6 may turn on by itself or short-circuits by itself causing fire in the middle of the night.
    Same for the aux fan in the V8's. These are PWM fans that always have power going to them, even when the car is off. The pulses from the DME make them spin, a failing component inside the fan motor can start the fire.

  7. #7
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    new aux fan assembly right? is that all I need?

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    Can't guarantee that fail condition won't occur again in the future. It IS a common failure mode for the PWM (your type) AUX Fans. The output transistor shorts from collector to emitter, and thus +12 volts ( max speed) is applied to the fan motor at ALL times (engine off or engine on). Only fix is to replace the complete unit with a quality unit. MANY units are for sale (see eBay for example). But I can't say they are quality units. Buyer beware!

    larrym3711
    2001 540iA Sport

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    Quote Originally Posted by LCIr View Post
    new aux fan assembly right? is that all I need?

    yes

  10. #10
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    Quote Originally Posted by JimLev View Post
    Same for the aux fan in the V8's. These are PWM fans that always have power going to them, even when the car is off. The pulses from the DME make them spin, a failing component inside the fan motor can start the fire.
    Not all are PWM by the way, only the later models are.



  11. #11
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    Quote Originally Posted by LCIr View Post
    new aux fan assembly right? is that all I need?
    Yes, and even though BMW brand is not perfect, I'd not even mess around with aftermarket brand.
    Again, install 2 smoke alarms and connect them together:
    - Let's say your garage is next to your dining room's wall.
    - Install the smoke alarms in such a way that they are on opposite sides of the walls, this way you don't have to run long wires.
    - Get the 120V smoke alarms type, this is the type home builders use to connect many alarms in parallel circuit in new home construction.
    When one alarm goes off, the rest go off.
    - The cost is about $8/alarm. No need to hook it up to 120V, a 9V battery is good enough. Very very easy set-up.
    Look it up on line.

    This will allow you to sleep better at night!

  12. #12
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    @cnn: I'll try to do that. Peace of mind is priceless.
    @larrym3711: That's what Im leaning to, replacing the whole aux fan assembly. I am looking at a BEHR brand aux fan, is this any good?

  13. #13
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    Check out Spal fans. Very high quality.

  14. #14
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    Stick to dealer Aux Fan. I know it is expensive but...

    - - - Updated - - -

    Another mod to think about.
    Somehow wire it in such a way that it can ONLY run if the key is in position II only.
    The Honda and Volvo Aux Fan is wired this way.

    By doing this mod, the Aux Fan cannot run once the key is out.

    Below is the diagram for 1999+ models. Fuse #75 is the circuit you want to be "switched".


    Last edited by cnn; 06-24-2013 at 02:56 PM.

  15. #15
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    so what you mean is even if I changed the whole assembly let's say OEM aux fan...it will still have the possibility of happening again?

  16. #16
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    Yes,

    But unlikely. As the Aux Fan gets older, things can happen.
    Brand-new Fan should be trouble-free for about 5-6 years.

    But to sleep better, you can install a relay in such a way that:

    * Circuit 30-87 is in series with the Positive wire that feeds the Aux fan 12V supply.
    * Circuit 85-86 is controlled by the ignition switch. Find a circuit that is ON ONLY when key is in position II.
    For example: 85 is grounded and 86 is ON ONLY when key is in position II.

    This way once you remove the key, the Aux Fan will stop running no matter what. This is how Honda cars work.

  17. #17
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    That's true. In my volvo, aux fan works flawlessly...I'll show the diagram to my mechanic and see what we can device out of it. Thanks!

  18. #18
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    I drew this generic photo to give you some idea to turn the Aux Fan into a switched circuit:

    * RED is the current flow to Aux Fan (1 is Fuse, 2 is relay, 3 is ignition feed, 4 is the Aux Fan Motor).
    * BLUE is the control circuit.



    E39AuxFan.JPG

    - - - Updated - - -

    For now, park the car outside, not in the garage.

    Car is cheap compared with a house fire damage.

  19. #19
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    more i read, the more every piece of the car needs to be replaced or modified......

  20. #20
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    Ok....so Im going to replace the whole aux fan assembly....I found a BEHR brand aux fan. Any experiences with it? Thanks!

  21. #21
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    There are quite a variety of aux fans out there....many parts houses sell one or more brands. It is not difficult to find discount prices on sites such as eBay. Certainly BEHR is a well known name, but I suspect it too is made for them by s third party at some offshore location, as it is for so many others.

    larrym3711
    2001 540iA Sport

  22. #22
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    Quote Originally Posted by fmzip View Post
    more i read, the more every piece of the car needs to be replaced or modified......
    +1000, reading on here sometimes get scary

  23. #23
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    This is just ridiculous. The Aux fan can run while the car is off? Someone needs to make a DIY to fix this.

  24. #24
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    I suspect the aux fan being able to run with the ignition off had a good beginning....that is...when you shut off your engine, there is still considerable heat transferred to the cooling system....raising an already high pressure system to an even greater temperatures AND pressures.. To the extent heat can be removed by running an ELECTRIC fan with a temperature probe, the system is self protecting against perhaps damaging conditions. When sufficient heat has been eliminated, the electric fan shuts down. The problem is, of course, is that if the unit shorts out (a fairly common failure) the fan runs continuously when it should be off. This is not only annoying but is guaranteed to run down your battery, and, may even catch fire (remember it has shorted out), potentially making for a very serious situation.

    larrym3711
    2001 540iA Sport

  25. #25
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    I just replaced mine at 140 k the amount of debris behind it are amazing. I bought a knock off fan and of course it rubbed against the shroud. Dremel tool to the rescue! It's loud as always but at least I know it works another wear and tear item to replace. Have a new shroud,will replace soon. Fast and easy job. Tim 99 528is,73 2002tii

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