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Thread: Auxiliary Fan Not Working

  1. #1
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    Auxiliary Fan Not Working

    was stuck in traffic a few days ago and after 45 minutes sitting still in 80 degree weather with my heater on, the temp gauge moved to 1pm, i pulled over and shut off the car, carefully let some water out to relieve pressure from hoses... after 30 minutes was all good, traffic subsided and drove home.

    Is not the Aux fan supposed to come on when the temp rises that high?

    Anybody have similar situations? fuse? relay? other?
    "...i haven't taken leave of my senses Bob, I've come to them..." -- Ebenezer Scrooge

  2. #2
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    The auxiliary fan saves the day when the radiator outlet temperature is 99C - at which point the engine temperature (as shown on the gauge) will be at the 3/4 mark. But, the auxiliary fan is not needed if the rest of the cooling system is operating correctly - and overheating in traffic usually means the viscous-coupled fan has failed or there is debris between the radiators - more info here (for the V8, but the V12 has the same system):

    https://www.meeknet.co.uk/e31/BMW_M6...ing_System.htm

    P.S. There is no need to reduce the pressure - the expansion-tank cap is a pressure relief valve
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  3. #3
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    Quote Originally Posted by Timm View Post
    The auxiliary fan saves the day when the radiator outlet temperature is 99C - at which point the engine temperature (as shown on the gauge) will be at the 3/4 mark. But, the auxiliary fan is not needed if the rest of the cooling system is operating correctly - and overheating in traffic usually means the viscous-coupled fan has failed or there is debris between the radiators - more info here (for the V8, but the V12 has the same system):

    https://www.meeknet.co.uk/e31/BMW_M6...ing_System.htm

    P.S. There is no need to reduce the pressure - the expansion-tank cap is a pressure relief valve
    thanks Timm, great information on your link!! by the way my clutch died on my fan last month and replaced it, i can tell easily that it engages because it makes the fan howl ! I will check the aux fan fuse and clean the fins...
    "...i haven't taken leave of my senses Bob, I've come to them..." -- Ebenezer Scrooge

  4. #4
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    Some years ago my aux fan was not working. Cause: low and high speed relay spades were oxidized, used some contact spray for the relays and the aux fan worked again. Also the plug of the wire which goes into the aux fan at the fan has to be checked, that can also be oxidized.
    Shogun tricks and tips for the E32 series are HERE!

  5. #5
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    Quote Originally Posted by shogun View Post
    Some years ago my aux fan was not working. Cause: low and high speed relay spades were oxidized, used some contact spray for the relays and the aux fan worked again. Also the plug of the wire which goes into the aux fan at the fan has to be checked, that can also be oxidized.
    which relays are they? last night my fuse #25 checked out fine... i have yet to open up the front cover to see the fan...
    "...i haven't taken leave of my senses Bob, I've come to them..." -- Ebenezer Scrooge

  6. #6
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    http://shark.armchair.mb.ca/~dave/BMW/e31/e31_91.pdf page 0670.0-01 shows you
    K21 normal speed
    K22 high speed
    page 0670.0-00 shows you the relay location chart in front power distribution box.
    Print those pages out and leave them in your glovebox, you need it more often. I printed these sheets out and used a marker pen and wrote down in each relay and module what it is. When I open the fuse box cover, I can see it immy
    Shogun tricks and tips for the E32 series are HERE!

  7. #7
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    Quote Originally Posted by shogun View Post
    http://shark.armchair.mb.ca/~dave/BMW/e31/e31_91.pdf page 0670.0-01 shows you
    K21 normal speed
    K22 high speed
    page 0670.0-00 shows you the relay location chart in front power distribution box.
    Print those pages out and leave them in your glovebox, you need it more often. I printed these sheets out and used a marker pen and wrote down in each relay and module what it is. When I open the fuse box cover, I can see it immy

    i dont have a K21 relay at all ! is this part of my problem then? the K22 relay looked ok, the prongs were a bit "browny" but i cleaned them...
    "...i haven't taken leave of my senses Bob, I've come to them..." -- Ebenezer Scrooge

  8. #8
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    Check the exact month and year the car was built. You mention 1990, but 1990 could be a 1990 model year or a 1991 model year, here all ETM by built year/month, check again with the correct ETM http://shark.armchair.mb.ca/~dave/BMW/e31/
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  9. #9
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    There is a resistor (0,47 ohms 100W) mounted on the fan. This resistor have been broken sometimes, check it.

  10. #10
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    Right from the start of production there were two relays for the auxiliary fan, K21 and K22 - and they were located as shown here:

    https://www.meeknet.co.uk/e31/Timms_...lay_Finder.htm
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  11. #11
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    Quote Originally Posted by Timm View Post
    Right from the start of production there were two relays for the auxiliary fan, K21 and K22 - and they were located as shown here:

    https://www.meeknet.co.uk/e31/Timms_...lay_Finder.htm
    im going to pick up both new relays...

    plus i did see that resistor, it looks intact and ok...

    furthermore, i cleaned out tons of debris (mostly leaves) from between the 2 rads... unbelievable!!

    thanks all !! will update soon...
    "...i haven't taken leave of my senses Bob, I've come to them..." -- Ebenezer Scrooge

  12. #12
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    Quote Originally Posted by starship1701a View Post
    im going to pick up both new relays...

    plus i did see that resistor, it looks intact and ok...

    furthermore, i cleaned out tons of debris (mostly leaves) from between the 2 rads... unbelievable!!

    thanks all !! will update soon...
    The resistor usually looks good, you have to measure it´s resistance with a multimeter it should be around 0.47 ohms.

  13. #13
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    replaced K21 with new relay... still work go on, granted its on a thermostat...

    but wont go on either when switching on the AC...
    "...i haven't taken leave of my senses Bob, I've come to them..." -- Ebenezer Scrooge

  14. #14
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    It's not on a thermostat as far as the A/C is concerned - if the compressor runs so should the auxiliary fan......
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  15. #15
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    Quote Originally Posted by Timm View Post
    It's not on a thermostat as far as the A/C is concerned - if the compressor runs so should the auxiliary fan......
    agreed this is also what i understand... and so...
    "...i haven't taken leave of my senses Bob, I've come to them..." -- Ebenezer Scrooge

  16. #16
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    Short the resistor, this will make the fan work at max power. If it starts working the resistor is broken which happens.

  17. #17
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    Quote Originally Posted by peake View Post
    Short the resistor, this will make the fan work at max power. If it starts working the resistor is broken which happens.
    tried to short the resistor, nothing... had the AC button on too.

    i just read another post where someone wrote that there's a sensor on the passenger side of the radiator... i suppose it gets hot to trigger power to the fan?

    short of ripping the entire fan out, not sure what else to do to get this elec fan running...
    "...i haven't taken leave of my senses Bob, I've come to them..." -- Ebenezer Scrooge

  18. #18
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    I was chasing the same problem at the weekend - no auxiliary fan and no compressor action. This is normally because the refrigerant pressure is too low and the compressor is inhibited (along with the auxiliary fan). But, I checked the refrigerant pressure and that was fine.

    One easy check is to see if the low-speed relay clicks - this is K21:

    https://www.meeknet.co.uk/e31/Timms_...lay_Finder.htm

    With the ignition in position II, snowflake button in and LED lit, fan speed on automatic (just right of OFF on the rotary control) the auxiliary fan should run. You can now remove K21 and if it is energised you will feel and hear the relay click as you remove and replace it - it is quite obvious.

    Have a good look at the relay, it has a diagram on the side of it and you can work out where the pins 30 and 87 are (they are marked underneath the relay) and you can short out the contact sockets and see if the fan runs - it should do.

    Don't forget though - if your air conditioning doesn't work then neither will the auxiliary fan run until you are dangerously overheating. If you overheat it isn't anything to do with the auxiliary fan.

    P.S. My problems were poor connections at the after-market auxiliary fan connector pair:



    ....and the compressor didn't run for exactly the same problem....how strange....
    Last edited by Timm; 07-23-2018 at 04:11 PM.
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  19. #19
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    Quote Originally Posted by Timm View Post
    I was chasing the same problem at the weekend - no auxiliary fan and no compressor action. This is normally because the refrigerant pressure is too low and the compressor is inhibited (along with the auxiliary fan). But, I checked the refrigerant pressure and that was fine.

    One easy check is to see if the low-speed relay clicks - this is K21:

    https://www.meeknet.co.uk/e31/Timms_...lay_Finder.htm

    With the ignition in position II, snowflake button in and LED lit, fan speed on automatic (just right of OFF on the rotary control) the auxiliary fan should run. You can now remove K21 and if it is energised you will feel and hear the relay click as you remove and replace it - it is quite obvious.

    Have a good look at the relay, it has a diagram on the side of it and you can work out where the pins 30 and 87 are (they are marked underneath the relay) and you can short out the contact sockets and see if the fan runs - it should do.

    Don't forget though - if your air conditioning doesn't work then neither will the auxiliary fan run until you are dangerously overheating. If you overheat it isn't anything to do with the auxiliary fan.

    P.S. My problems were poor connections at the after-market auxiliary fan connector pair:



    ....and the compressor didn't run for exactly the same problem....how strange....
    strange? aint nothing strange about this car...

    more good advice thanks Timm, yes my AC doesnt work, the refrigerant is low or empty... purchased aftermarket refrigerant kit, gonna try to install it again...

    im also thinking i should reconnect the resistor then?
    "...i haven't taken leave of my senses Bob, I've come to them..." -- Ebenezer Scrooge

  20. #20
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    That's the reason your auxiliary fan isn't running - it doesn't need to as your A/C doesn't work!
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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