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  1. #1
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    Help Auxillary Cooling fan doesnt run.......

    I replaced the fan about a year ago and it worked fine. Recently I noticed it wasnt kicking on, I know that its supposed to run when the air cond. is turned on. At any rate I replaced the temp sensor on the passenger side of the radiator, checked the fuse , even that pisser of one #75, checked the relay - all fine. I disconnected the connector from the temp sensor and jumpered across it and the fan runs fine and at multiple speeds. Even when the car warms up and the ac is on, it wont run. Any ideas?


  2. #2
    greazedjebus
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    Tip for fuse #75 & #76

    I'm chasing a similar problem, so I'll be interested to read other's suggestions and how you end up resolving your issue.

    The aux fan and blower fuses are a real PIA to get to and the write-ups (bmwtips.com has one in Tips & Tricks) I've seen are really only helpful in locating them - good luck getting them out and, even worse, putting them back in. I filled my swear jar trying and eventually succeeding in removing and replacing #76 when my FSU crapped out. (Of course, the fuse was fine and replacing the FSU solved the problem!) There is an easier way...

    Take off the trim panel and have a peek to see where the fuses are hidden. Once you have a visual of where the fuses are located, get off your back and open the glove box (this gives more clearance at the back side). Now, kneeling outside the car, reach up behind the glove box and find them by feel - you'll be surprised how much room to manoeuver there is. It took me all of 25 seconds to remove the fuse, see that my problem wasn't that simple (or cheap), and put the fuse back in place. I hope this tip saves someone some grief - especially since fried FSU season is almost upon us!

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    What year and engine? There are 2 or 3 different (

    setups for controlling the aux fan. The newer cars with the DME controlled variable speed aux fans do come on when the A/C is switched on, but if you have the 3 speed fan it may turned on the low relay by the DME and then when the coolant gets hot enough to trip the temp sensor switch the fan speeds up.

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    Re: What year and engine? There are 2 or 3 different (

    Car was built in april of 1998, its a 528i

  5. #5
    Jim Cash
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    Re: Help Auxillary Cooling fan doesnt run.......

    Your year of car has the old style "3 speed" fan that has three different input circuits to activate the fan

    BUT - if you say the fan operates when you short the leads at the rad temp sensor switch then it is not the fan, relay or fuse.

    Especially if you say you can get different speeds when shorting the leads at that connector. That connector will only activate 2 of the 3 speeds (low and high) and if you are getting the low speed to operate then all the resistors are OK (resistors are the common problem)

    Again - if you have a new fan then you should also have new resistors and the motor should be good and no blockage behind it (but do manually spin the fan to make sure it is not stuck on something)

    When you turn on the AC are you actually getting the AC to operate?
    The engine idle should go up by about 100 RPM - if it does not then the engine computer will not send the OK signal back to the climate control panel - and it is that panel that sends out a signal (in parallel to the low speed temp switch) to activate the low speed relay/

    So make sure the AC is actually activating.
    Also - is your outdoor temp reading correctly? That temp signal goes to the climate panel and must be above 10C for the AC to operate.

    Cheers
    Jim Cash

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    Re: Help Auxillary Cooling fan doesnt run.......

    The ac is working fine as is the outside temp. There is no blockage of the fan it spins freely.

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    Re: Help Auxillary Cooling fan doesnt run.......

    Here something to try to rule out any bad resistors definitively.

    I have the same car 528ia (04/98), and when my aux fan went bad, I tried the same method to diagnose which resistor line was bad, if any at the connector, but I got a little confused jumping the various wires at the connector and the fan would run.

    So, even though you jumped the connector wires and the fan was running (like mine did), try jumping/by-passing each resistor, in turn, by stripping a small portion of the wires before and after each resistor, and clip a piece of wire to by-pass the resistor.

    I found one was bad and I just left the jumping wire taped across the resistor, (which BTW I hope doesn't have any long-term ill effects until I replace the entire assembly in the future; Jim Cash, if you happen to read this, I would appreciate any comment to this patch.)

    It's been about 30K miles since.


  8. #8
    Jim Cash
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    Try

    Try pulling the Climate control panel and grounding the Blacm/red lead on pin 18. That is electrically the same as grounding the lead at the rad temp switch - those leads are "bridged" together at a "solder connector" up behind the glove box.

    If it starts when you ground the lead at the back of the climate panel but does not operate with the the panel then I would suspect the panel.

    Also double check fuses 20 & 7

    Cheers
    Jim Cash

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    Larry
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    Re: Try


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    How do I do that..

    how is the best way to remove that. I have looked at several posts and it looks like a nightmare to put all the springs and stuff back together.

  11. #11
    Jim Cash
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    Re: How do I do that..

    No - all you do is pull the panel out and go to the connector on the back.

    Remove the MID panel (turn small screw behind the Vol knob while pulling the MID panel outward on that side - then put your fingers in behind the climate panel and push it outward - friction fit.

    Connector is easy to remove from back of panel

    Cheers
    Jim Cash

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    Damn- No Luck.....

    I grounded pin 18 and tried it with the key in all positions and the fan did not turn. I disconnected the plug again from the temp sensor on radiator, put 12V to it and the fan runs. Double checked the fuses....any other ideas? I relly dont wnat to tke it to the shop but with summer coming on I may have to.

  13. #13
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    There are 3 relays in this fan circuit. When you (

    ground wire 18 (or the A/C is turned on) relay K21 (normal speed relay) under the pass side cabin filter (DME) box energizes, this relay supplies 12 volts to the resistor pack on the aux fan. This relay could be bad.
    The wire from the relay K21 (relay terminal 87, or relay socket pin 2) goes to the resistor pack, it should be black/brown.

    The temp sensor connector wires info:
    You should be grounding (not applying 12 volts) to the temp sensor wires.
    At the temp sensor connector pin 2 (brown in ground).
    Pin 3 should turn the fan on above 91C, this is the same wire that comes from the HVAC panel, #18 (or when you grounded it)

    Pin 1 black/gray controls the high speed thru relay K201 and switches above 104C.

    There is a pressure switch for the R134a that controls K22, as long as the pressure is below 17.5 bar it will control the mid speed. K22 (relay terminal 87, or relay socket pin 2) goes to the resistor pack, it should be black/green.
    Good luck, check K21 first.

  14. #14
    Jim Cash
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    Woa - follow JimLev's info

    Not sure how you are getting the fan to run by putting battery on a connection at the temp sensor.

    Just to double check - this temp switch is the one on the upper side of the rad - correct?

    There should be 3 wires on it

    - brown is the ground lead
    - Black Red is what feeds the ground to the Low Speed fan relay
    - Black Green is what feeds the ground to the HIGH Speed fan relay

    All that temp switch does is close the correct contact to feed the ground to one or both of those leads.


    Where are you putting the battery when you get the fan to run?? That may be important to know to try to determine what is happening. Also when you say the fan runs does it seem to be low or high speed (high is quite noisy)


    If and when you are grounding the leads we described above to the low speed one first - if you ground the high speed lead when the fan is stopped then the high starting current can blow the fuse.

    As Jim mentioned - all you are doing is grounding the signal lead to one of the 3 relays - it is the relays that then operate and send power to the fan - through the resistors to get the first 2 speeds.

    Cheers
    Jim Cash

  15. #15
    Larry
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    Ok - heres where I'm at

    the plug that goes into my temp sensor has 3 wires. black with white stripe, brown, and black with red. The brown wire is the middle pin. I grounded the black/red- nothing. Grouning the black/white the fan runs. I cannot tell what speed since I have no reference.

  16. #16
    Larry
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    ALSO

    To get the fan to run on a 12V supply I put 12 V to the bl/red and blk/white wires. Polarity works both ways but the fan spins the same direction regardless of which lead I put pos and neg to.

  17. #17
    Larry
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    Relay

    How do I determine if its the relay, when I grounded pin 18 at the climate control unit I hear a faint click from uner the passenger side cabin air filter. I assume thats the relay clicking.

  18. #18
    Larry
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    Which Relay

    Which relay is K21 there are about 5 of them in there?

  19. #19
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    Yes, that's the relay, Have you pulled it out (m)

    to look at it or swap it?

  20. #20
    Larry
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    Which relay is it- there are 6


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