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Thread: Pusher (Aux) Fan dosen't come on

  1. #1
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    Pusher (Aux) Fan dosen't come on

    The car overheats when in traffic or at a stop light in hot weather. When moving the temp is fine.

    Well rather than resurecting an old thread from about a year ago, I re-read it and did all the tests on the main fan and clutch. The main fan has no wiggle in it, and does not spin freely, although I can spin it about 1/3 of a turn with a decent push, and it spins faster as the engine warms up. When cold i can stop it by easing my hand against it, when hot, I'm not even going to try....it's spinning with a vengance!

    So I think my issue is with the pusher (aux) fan that you can see right behind the grill. This fan never comes on. I'm assuming as the car heats up (at a stop light or in traffic) this fan is supposed to come on to sort of "piggy back" onto the main fan? Well this is when the car starts to overheat. I can usually put the car in neutral and keep the temp down by increasing the revs, but of course I'd rather not have to do that. Sometime in '98 the resistor was dropped from the fan so I don't have a resistor to check. I checked the plug and it seems fine.



    06 PUSHER FAN 1 09/1998 10/2005 64546921942
    06 PUSHER FAN 1 09/1998 64546921383

    Looks like there are two pusher fans to choose from that cover my year....



    Is there a way I can put power to the Aux fan manually and check to see if it works? If I can, at least i'll know if it's functional or not. That way I'll know if I have to replace it, or move on up the line to the sensors and controls to diagnose the problem.

    Thanks
    Last edited by Wildroot56; 04-02-2010 at 07:51 PM.

  2. #2
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    Turn your AC on - the Aux fan should come on immediately.
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  3. #3
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    The auxiliary fan will only start running (unless the AC is ON) when the temp gauge hits the 3/4 mark. The viscous-coupled fan should do most of the work and it is usually only when this fails that the aux fan saves the day.

    It could be that your cooling system needs a good flush as it sounds as if it is not running efficiently if the viscous fan is operating correctly....
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  4. #4
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    Oh the A/C is on until I start overheating...I've let the car get hot with the A/C on and then go and check on the Aux fan and it's not ever running.
    I'd like to test the Aux fan independently to see if it even works. The motor may be shot. Not sure how to test it though.
    Last edited by Wildroot56; 04-02-2010 at 08:37 PM.

  5. #5
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    At the moment my Aux fan doesn't kick in at the first stage, it will only kick in once I've revved up to about 4,000rpm. I just had the resistors replaced and it made no difference so now Im gonna have to try replacing all the relays that have anything to do with the Aux Fan.

  6. #6
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    Quote Originally Posted by Aindriu View Post
    At the moment my Aux fan doesn't kick in at the first stage, it will only kick in once I've revved up to about 4,000rpm. I just had the resistors replaced and it made no difference so now Im gonna have to try replacing all the relays that have anything to do with the Aux Fan.
    Mine dosen't have a resistor so that's not an option. I want to start at the end with the fan itself and see if it's functional, then move down the line till I find the problem. I think the motor on the fan is shot, but I want to make sure before I pony up to replace it.

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  8. #8
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    Does your fan clutch (engine) ever turn on? Could be you need a new one

    http://www.oembimmerparts.com/catalo...47/4603906.htm

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  9. #9
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    My MAIN fan appears to works fine, the one connected to the fan clutch. As I said in the 1st post, the hotter the engine, the more robust the main fan spins. The fan clutch controls the power or speed of the main fan, right?

    The Aux fan however, NEVER spins. When the car temp is getting close to the red with or without the A/C on, the Aux fan does not turn. Is this what's causing me to overheat?
    Is there a way I can put a test on both sides of the Aux fan connector to put power on the Aux fan to see if will turn, and test the other side of the connector to see if it's getting a signal to turn the aux fan on?
    Last edited by Wildroot56; 04-03-2010 at 10:21 AM.

  10. #10
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    not sure, but adding 12V should get it to spin, if not $$

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  11. #11
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    Quote Originally Posted by Wildroot56
    06 PUSHER FAN 1 09/1998 10/2005 64 54 6 921 942 {ENDED} (FIXED)
    06 PUSHER FAN 1 09/1998 64 54 6 921 383

    Looks like there are two pusher fans to choose from that cover my year....
    Nope, there's only one...be careful when looking at the part database...follow the line all the way over to the far right and you'll see that part nbr 64 54 6 921 942 is ENDED (no longer available) and the part nbr on the next line down is what BMW sells in it's place.

    Below is some info that you've already discovered...and there may be some other info that may help you further.

    Sounds like you're on the right track...just find the electrical harness and apply power to see if the fan will kick on (see image below for "power & ground" location).

    (this info is for 99-01 E38s w/M62TU engine which has a VARIABLE speed aux fan...does not apply to the 95-98 740i/iL w/M62 engine which has a 2 speed aux fan)




    Last edited by Qsilver7; 04-03-2010 at 11:55 AM.
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  12. #12
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    Quote:
    "When the vehicle is first started, the ECM activates the electric fan briefly at 20% of its maximum speed, then switches off. This is for diagnostic monitoring. The voltage generated by the fan when it slows down (acting as a generator) must match the stored rpm values in the fan output stage to confirm that the fan is operating correctly"
    So, does this basically mean that the Aux fan is activated for a short time every time you start the vehicle with cold/hot engine?
    Mine does not spin when I start the vehicle, nor it spins when I turn the A/C on.
    Last edited by Edwin NL; 05-26-2010 at 03:51 AM.

  13. #13
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    In for results my fan NEVER comes on. Regardless of engine temp or AC use.

  14. #14
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    I've got a Mercedes Indy right next to my carwash, took the car over to him and asked about the Aux fan...(I assumed Mercedes had them as well) Anyway he connected up to a power source from the car and tried to make the aux fan turn by touching the leads to the connector and he said for sure the fan was shot. It moved about an inch and that was it. So although I MAY have other problems down the line with sensors etc...I'm going to start with replacing the aux fan first.

    For some of you guys up north, your aux fan may not work and it may not be something that you notice. Down here in S.Texas though, you'll know in a hurry if some portion of your car that has to do with cooling is out of wack.
    Last edited by Wildroot56; 04-03-2010 at 05:49 PM.

  15. #15
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    Quote Originally Posted by Skinny Puppy View Post
    In for results my fan NEVER comes on. Regardless of engine temp or AC use.
    Drove the car for about 15 min in the city with the A/C on, parked, and with the engine running quickly checked the Aux fan and it was spinning,actually coming to a stop. So, now I have peace of mind that the fan is functioning.

  16. #16
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    Quote Originally Posted by fraerok View Post
    Drove the car for about 15 min in the city with the A/C on, parked, and with the engine running quickly checked the Aux fan and it was spinning,actually coming to a stop. So, now I have peace of mind that the fan is functioning.

    Yeah, that's good....I remember now that i think of it hearing my fan running after I shut the car off, would run for 5 min or so. It took my car overheating to realize it wasn't running anymore. You'll find out in a hurry if you live in the south!

  17. #17
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    i know this may seem goofy, but mine wasnt running and i checked the fuse and it was blown....replaced it and has worked ever since.....not sure why the fuse was blown but it was when i first bought my car....replaced fuse and have put 50k more on it without prob....just a thought

  18. #18
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    Quote Originally Posted by cerizoman1 View Post
    i know this may seem goofy, but mine wasnt running and i checked the fuse and it was blown....replaced it and has worked ever since.....not sure why the fuse was blown but it was when i first bought my car....replaced fuse and have put 50k more on it without prob....just a thought

    Where was the fuse located?

  19. #19
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    front fuse box...under the hood on pass side....i'll check which fuse and repost...

    on my 95 740i, its listed as fuse 9,20,34,38...not sure which one i replace, one was blown....oh, btw, have you checked your thermostat out, how hot of weather do you notice that it starts to peg the temp....just curious
    Last edited by cerizoman1; 04-04-2010 at 11:32 AM. Reason: Automerged Doublepost

  20. #20
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    Well I ordered the fan a few months ago off ebay and let it sit in the garage for a few months. I finally got tired of the overheating (it's getting hot here) so I planned a day to do the switch. It took me all of 45 minutes to pull off the bumper, replace the fan and reinstall the bumper! Very un-BMW like! All fixed...no overheating anymore!

  21. #21
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    Your fan clutch is probably junk. The auxiliary fan is just that auxiliary. When the temp gauge gets over 1/2 you should be able to hear the fan pulling air. If you rev it up and don't hear it then its inop. You most likely also need a new aux fan too. You will need it to get cold air from the ac at idle and keep the ac pressure from going too high. Any time the ac is on and the outside temp is over 60 the aux fan should be running. Hope this helps.

  22. #22
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    Quote Originally Posted by bmwbob89 View Post
    Your fan clutch is probably junk. The auxiliary fan is just that auxiliary. When the temp gauge gets over 1/2 you should be able to hear the fan pulling air. If you rev it up and don't hear it then its inop. You most likely also need a new aux fan too. You will need it to get cold air from the ac at idle and keep the ac pressure from going too high. Any time the ac is on and the outside temp is over 60 the aux fan should be running. Hope this helps.
    You misunderstand....

    I installed a new aux fan (pusher fan) and all is working properly now. No more overheating, aux fan is running when it's supposed to...all is good now. And surprisingly it took all of 45 minutes to pull the front bumper, remove the old fan, install the new one and reinstall the bumper. Easiest job on this car I've ever done...easier than doing an oil change!

    Thanks anyway though

  23. #23
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    The fan should kick in after about 30 sec when the AC is on and your car is idle

    Have a technical question, don't send me a PM but post it on the board so others can benefit from it!

  24. #24
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    What did I misunderstand?

  25. #25
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    45mins? That is very un-BMW like. Hopefully this summer it's not 100+ like last summer when I would see 109* on my outside temp. The a/c in these cars cools the fastest of any car that I have ever been inside which is a HUGE plus here.

    BTW wildroot56, where abouts in San Antonio are you located? I'm just up I-35 in Schertz on the NE side.
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