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Thread: E39 Aux Fan Service - READ ON

  1. #126
    Join Date
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    1999 528i

    Aux fan circuit draining battery

    Hi, I've isolated it down to something in the Aux Fan circuit that is causing my battery to die after a few days. Any idea what it might be (resistor pack or relay)? When I disconnect the fan connector (just in behind the grill and in front of the aux fan), the battery no longer drains/dies. I'm not sure if the resistor pack is shorting somehow or if one of the relays is kicking on occassionally. Any help would be much appreciated.


    Quote Originally Posted by PENER View Post
    as many of you know, auxiliary fan failure is one of many weak points on most bimmers. just to remind, it's the electric fan mounted in front of the A/C condenser (that is located in front of the radiator) that sometimes makes our cars sound like an airplane during acceleration.

    the aux fan is always on (low speed) whenever A/C compressor is on, to cool off the refrigerant flowing through the condenser (using A/C without properly functioning aux fan can cause compressor failure). when it's very hot, the fan may go into medium or rarely high mode, which really sound like an airplane, to provide some extra cooling for the cooling system.

    additional info: the connector for the fan consists of four wires:
    brown-ground
    blue-12v direct to fan, high mode
    red-12v through single resistor to fan, med mode
    black-12 through both resistors (in series) to fan, low mode

    you can notice the first problems with the fan if it's not coming on when A/C compressor is on. the possible reasons of this are:
    -bad fuses: #7,20,22 or 75, the last one being under and behind the glove box comp.
    -failed resistor(s)
    -failed radiator temp switch
    -failed fan motor
    (-rarerly failed relay)

    most often it is either bad resistor pack or fan. it's worth mentioning that a failed resistor may often cause the fuses to blow. the reason for that is that with failed resitors the fan is not working on low speed and on the occasions it is kicking into high there is too much current draw.

    to check whether it's the mulfunctioning resistor, (assuming all fuses are OK) you can just jump pins at the temp switch, or connect 12v DC directly to the fan connector (brown-ground, blue-12v positive). if the fan kicks in high mode, the problem is the resistor pack ($50-60).
    if the fan is not working at all, the second method (direct 12v) will tell you whether the fan motor is the culprit.

    most online vendors want almost $60 for the resistor packs and the fan motor alone is a whooping $200. preety steep, considering the entire fan assembly costs $300, though seeing the size of the motor and how powerfull it is, no wonder it costs so much.
    below is the pic of the fan motor from one of my favorite online vendors, charging around $190 for it


    however, I have been able to spot a tremendous deal for the very same motor at Autozone. the same fan (SIEMENS PM9047) they sell for ONLY $82!!!
    below it the fan motor I ordered from AutoZone

    as you can see, it's the very same fan, and actual replacement part for our cars. comes terminated with the prongs that slide into the connector and even has a part of the blue wire stripped in place where resistor packs connect to it

    some pics of my old fan and new replacement



    (I'd like to add here, that upon removal of the old fmotor, I found it to be still spinning with 12v put to it, although it did not work during the earlier tests. however many owners can confirm similar results with their old units. but now, knowing that you can get the new motor for only $82, it's no brainer...)


    replacement of the fan resistor pack or entire fan assembly requires the bumper to be removed first together with both headlights and the (kidney) cowl. sorry for the crappy pic (low light conditions) BTW in case someone wonders where is the Secondary Air Pump (bottom left corner of the pic), it's been replaced with new type pump and retrofitted under the hood.


    good luck

  2. #127
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    Just replaced whole aux fan unit. Not a hard job, old one was dead.
    Worth noting, got a unit from AutohausAZ, and it came with resistor pack installed. A Behr OEM, perfect fit, shipping included for $158.

  3. #128
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    Quote Originally Posted by peterintheyvr View Post
    Hi, I've isolated it down to something in the Aux Fan circuit that is causing my battery to die after a few days. Any idea what it might be (resistor pack or relay)? When I disconnect the fan connector (just in behind the grill and in front of the aux fan), the battery no longer drains/dies. I'm not sure if the resistor pack is shorting somehow or if one of the relays is kicking on occassionally. Any help would be much appreciated.
    Score! Finally found someone having the same issue as I am with the aux fan. According to your signature, you have a 1999 e39 (as do I) which means that there is no resistor pack and no set of three relays that control fan speed. Input to the fan is simply ground, 12V, and a PWM signal from the ECM that controls fan speed. I am assuming the problem is something to do with the fan motor/controller that is causing it to draw current (about .5A) when the car is off, in which case I'm guessing that the most reasonable approach is to just replace the fan ... but I'm not certain yet.

    -Doug

  4. #129
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    Im at my wits end! I have replaced both reistors, tried 2 different BRAND new relays in the ebox, and ALL fuses in glovebox are good and fuse 75 is good. The fan low speed only comes on when i remove the relay and jumper pins 87 and 30, i can make high speed come on by pumping the pins at the temp switch connector at the radiator. What is going on?? Does the coolant have to be at a certain temp for even the low speed to kick on? maybe the DME measures this?
    Electric Fan conversion, 840Ci thermostat, Dinan style CAI,de-screened MAF, Dinan transmission chip, 255lph LS1 fuel pump, drilled slotted rotors, 3.15 differential, Bel rx65 radar (hard-wired). Hemi Killer!

  5. #130
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    e61 touring RIP e39 wagn
    Don’t know if it’s specific to your car , but you get the idea of the wiring and switches and the relay.

    Low speed
    IMG_8841.JPG

    Medium speed
    IMG_8842.JPG

    High speed
    IMG_8843.JPG

  6. #131
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    2003 BMW 540im

    Aux fan had no plugs and f***** wiring

    So I have a 2003 540i that has been overheating in traffic at first I thought it might be the fan clutch, and still haven't checked the fan clutch while the car is warmed up, but while poking around the auxiliary fan I found that my wires have no plugs on either end and whoever I got this car from nutted two of the three wires on either side together and left the other two unutted. I only have 6 wires, a red and yellow, brown, and black from the sensor switch and a red, green, and black from the fan. The red and yellow wire was nutted to the red wire and the green to the black. When I touch the brown wire that is left over to the black wire coming from the fan the fan spins at what I assumed to be its highest speed like it's on crack this happens whether my key is in and on or laying on the grass next to me also the wires heat up. I tried other combinations and got either nothing or the fan trying to spin backwards... any answers?

  7. #132
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    Quote Originally Posted by jjones540 View Post
    So I have a 2003 540i that has been overheating in traffic at first I thought it might be the fan clutch, and still haven't checked the fan clutch while the car is warmed up, but while poking around the auxiliary fan I found that my wires have no plugs on either end and whoever I got this car from nutted two of the three wires on either side together and left the other two unutted. I only have 6 wires, a red and yellow, brown, and black from the sensor switch and a red, green, and black from the fan. The red and yellow wire was nutted to the red wire and the green to the black. When I touch the brown wire that is left over to the black wire coming from the fan the fan spins at what I assumed to be its highest speed like it's on crack this happens whether my key is in and on or laying on the grass next to me also the wires heat up. I tried other combinations and got either nothing or the fan trying to spin backwards... any answers?
    The Aux fan has nothing to do with overheating, it is to keep the air conditioning condenser cool.
    Electric Fan conversion, 840Ci thermostat, Dinan style CAI,de-screened MAF, Dinan transmission chip, 255lph LS1 fuel pump, drilled slotted rotors, 3.15 differential, Bel rx65 radar (hard-wired). Hemi Killer!

  8. #133
    JimLev's Avatar
    JimLev is offline Artifically Aspirated Moderator
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    If your Aux fan isn't working and you have the AC on it can overheat, especially in the summer.
    Your Aux fan should only have 3 wires, +12v, ground, and a PWM wire that controls fan speed from the DME.
    Sounds like someone used fan from a non tu engine or used an aftermarket fan.

  9. #134
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    I can't speak for the older style 3 phase fan but for the newer variable speed electrical aux fan there is a way to test if it's working using INPA.

    Strangely it's NOT found by selecting E39 - 5 Series --> Body --> Air conditioning IHKA IHR

    Instead you can get to the test by choosing E39 - 5 Series --> Engine --> (Choose your Engine Type)

    In my case this is ME 7.2 for M62 MJ 99

    Once in the main menu choose <F6> Activate --> <F2> Activate relay TEV --> <F3> el. fan

    If the fan is working you'll hear it click a few times in the first 5 seconds before it spins up and increases speed to max over about 15 seconds or so before cutting out and slowing down to a stop.

    If the fan works it will point to the culprit for the AC not working elsewhere... In my case to the system not having enough gas pressure.

    This can also be verified in INPA...

    E39 - 5 Series --> Body --> Air conditioning IHKA IHR

    <F5> Read Status --> <F1> Analog input

    The voltage for the pressure sensor is how the DME determines the pressure as one of the conditions that must be met for activating the AC compressor clutch via a final stage control.

    e39_IHKA.png

    I would have attached the whole document for the 2001 changes to models that this image is from but it's over 1MB and it gets blocked.

  10. #135
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    Quote Originally Posted by siny528i View Post
    Hello guys,

    Here's what I ve learned (thanks edjack from UnofficialBMW and Jim Cash from RoadFly) with some of my editing:

    Double Temperature Switch 91/104CEL (located on Radiator) activates the AUX Fan when coolant reaches above average temperatures:
    91C - Low speed
    104C - High Speed

    AUX Fan operates on 3 modes: LOW, MEDIUM and HIGH.
    NOTE: Newer E39's may have a variable speed fan and these tips may not be exactly what you're looking for.
    These tips are accurate for troubleshooting a 1998 540iA with a Nov 97 build date.

    AUX Fan comes on at LOW mode/speed whenever the AC is ON by an input from the AC controller and the engine computer combined AND the outdoor temp is above 10C - as shown on the display in the instrument cluster
    AND it supposed to stay on ALL THE TIME.

    Two days ago in order to check my newly installed AUX Fan I:

    - Disconnected the 3 wire harness that goes to the Double Temperature Switch 91/104CEL (located on Radiator):


    - Started the car;
    - Using small paper clip...


    ...I connected BROWN wire to the BLACK wire with RED Stripe - AUX Fan started to spin at MEDIUM speed;



    - Then
    I connected the BROWN wire to the BLACK wire with the WHITE Stripe - AUX Fan started to spin at HIGH speed;


    - Shut the car down and reconnected the harness to the switch.

    By jumpering at that point you are operating the relays that provide the power source to the fan.
    Relays are in the E box (under the passenger side microfilter).


    So my AUX Fan is Ok, but I wish I knew this trick and used it on my OLD one...

    IF the Aux fan did NOT run at any speed, then I would first suspect that a fuse is blown.
    IF you've checked the fuses then motor may have failed.

    IF the AUX Fan only worked on the highest speed, then I would suspect that one or both of the resistors or relays that control the lower speeds have failed (no resistors are used for the highest speed, but a relay is).The resistors that control the lower speeds are located on the AUX Fan Assembly.

    IF you are experiencing overheating and the fan worked flawlessly, maybe the temp sensor (the one that you disconnected to jump wires at) has failed.

    PS. Yesterday morning it was moderate outside. About 52F. I started the car and my AUX Fan went ON at LOW speed.
    I saw its spinning like this first time since I bought my car in 2007. Or maybe I've never noticed...
    I just wanted to say I used your method of testing the fan (after I installed the same unit you did with no signs of life) and it worked! It does not turn on on its own, so that’s a mystery, but at least now I know the fan itself works on both speeds and it isn’t defective. Did you find out why it doesn’t turn on on it’s own? I replaced the temp switch and checked the fuses (the relay not yet) but it won’t come on. My ambient temp sensor is missing, but upon further inspection I realized the ac high side pressure switch is broken (literally, idk who did it and how). Could these cause the inability of the fan to function on its own?

  11. #136
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    If the fan and resistors are good then I'd check the relays.

  12. #137
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    Quote Originally Posted by Junglist View Post
    If the fan and resistors are good then I'd check the relays.
    Cool thanks!

  13. #138
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    I just replaced the entire fan assembly on my 2002 530i. The fans on the earlier 528 models are different than the later model 525/530/540 in design. Here's the DIY guide for the replacement, which involves removing the front bumper.



    link: https://youtu.be/CazRTB9J0uw

  14. #139
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    Hello all, hate to revive a dead thread like this but I am having issues with my aux fan as well.
    My car is an 02 540i. The fan does not turn on at all, even with A/C on in 100 degree (F) heat. The fan spins freely, and it does spin on start up for computer test. No errors are thrown in the computer either.
    Where should i look first?

  15. #140
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    Jump back to Post #18 as your's is a later model with a different Aux fan than the earlier "preface lift" models. The DME sends a square wave signal to the fan to increase or decrease speed. There is always 12volts at the motor. IF NOT then check/replace fuses and relays. Any scanner (Foxwell 510 for example) will show you where the fault is. Fan assembly, Fuses (NO POWER) relays (no Power).

    Get a scanner, a volt ohm meter and TEST, don't guess.
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  16. #141
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    I thought I would add that I made a thread about repairing the motors for free, the title is "Fixing a Early E39 / E38 Auxiliary Fan / Pusher Fan Motor For Free".

  17. #142
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    I have read this entire thread and trying to figure out what is happening with my Aux fan. In short my 01 525 overheated I found the 19yo radiator developed a crack. Replaced the radiator hoses and thermostat as well as installed an electric Spal fan.

    Using an Ultragauge my temps max around 215F which lead me to check my Aux fan. I noticed it was not spinning when I would turn on the AC. If I turn the AC on and disconnect the fan and plug it back in it sometimes spins for a bit but then stops. I am hoping its doing this because of a loose wire or maybe a failing fan.

    I ended up getting a new Behr fan nd want to test the fan before removing the bumper. With the car and AC running I try to connect it but the fan does not spin at all. It could be due to not having a lot of slack and a loose cable but could I be doing something wrong? I have tested the connector with a multimeter and was able to detect 12v and ground. I am going to borrow a multimeter that can detect Hrz to see if I am getting a PWM signal. Luckily its getting into winter and I still have the electric fan but I would still like to get this figure out.

  18. #143
    JimLev's Avatar
    JimLev is offline Artifically Aspirated Moderator
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    Welcome to the forum CFLip2X.
    With the AC on the aux fan isn’t going to come until the temp sensor in the lower radiator hose gets hot enough for the DME to send PWM signals to the aux fan.

  19. #144
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    Quote Originally Posted by JimLev View Post
    Welcome to the forum CFLip2X.
    With the AC on the aux fan isn’t going to come until the temp sensor in the lower radiator hose gets hot enough for the DME to send PWM signals to the aux fan.
    Thank you. The car should have been up to temp I tested it after my drive to work. I did replace the sensor the old one had a bad o-ring so decided to get an extra since I was not sure of the type of ring. Even if it is not up to temp I should be able to connect the old one assuming it still works and just use a heat gun to warm it up and trick it switch on the fan. I have been so busy haven't had time to test with a multimeter will try today.

  20. #145
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    AUX Fan comes on at LOW mode/speed whenever the AC is ON by an input from the AC controller and the engine computer combined AND the outdoor temp is above 10C - as shown on the display in the instrument cluster AND it supposed to stay on ALL THE TIME. In other words, if you turn AC on while its LESS than 10C (50F) outside it will NOT engage, if more than 10C (50F) - it will...
    Last edited by siny528i; 11-12-2020 at 10:28 PM.
    BMW CCA 434493

  21. #146
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    Hi,

    Saw a fan error:



    Fan moves alright by hand but will only jump a little when activated with INPA (80% here):

    https://youtu.be/HMjtZRVaseU

    Is there something else to check or is the fan surely broken?

    Thanks.

  22. #147
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    I posted this in another thread recently and seems it belongs here too:





    The DME will check the operation of the aux fan at startup and periodically during operation. If a fault is detected (doesn't move at startup test) or fails during operation, it will disable A/C

    The aux fan (and A/C) will also not run if the car is too cold. So, if your ambient temperature sensor is faulty - the car will think it is -40 degrees outside, and it won't run the A/C OR the aux fan.

    The most common failure mode I have seen regarding PWM fans is the control wire, they often get brittle and break near the fan connector. They may work intermittently. This can often be diagnosed with INPA by commanding the fan on and then adjusting the PWM fan wire, moving it around - if some positions it works, others it doesnt, the wire is the problem.

    I see about 5 wire failures for every other type of failure related to the aux fan. It's always the first thing (along with ensuring ambient temp is reading correctly) I check on cars with A/C faults or aux fan faults.

    The aux fan can cause overheating. The fan clutch isn't always enough to cool the engine on it's own. It's usually enough to keep it from going nuclear, but if it's hot enough, a lack of working aux fan can cause the car to exceed the intended operating temperature of the engine. It is a "supplementary cooling fan" per BMW. Used for A/C, but also for cooling.


    Quote Originally Posted by lowlife89 View Post
    Hi,

    Saw a fan error:



    Fan moves alright by hand but will only jump a little when activated with INPA (80% here):

    https://youtu.be/HMjtZRVaseU

    Is there something else to check or is the fan surely broken?

    Thanks.
    As it sounds it works intermittently, I would check the PWM fan control wire (the small wire, it goes to DME X60004 pin 4)

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