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Discussion Starter #1
i already troubleshooted everything for the aux fan to kick on. everything is fine, that 50amp fuse was fine, the ecm to fan was fine, we used a snapon computer tool to manually turn it on and we used a power probe and multimeter to check for the hz. all of that checked out fine. coolant temp sensor on lower radiator hose is new too. outside temp sensor is new. anyway to fix the aux fan? or is it a must replace?
 

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BMW forever
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You have the computer controlled fan, so it is a replace item. You could open the motor up and have a look but most if not all will say it is a lost cause.
 

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Verify that the fan is not jammed with debris. If you can move the blades, mjallou11 is likely correct.
 

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Discussion Starter #4
i will do that. good call. although i remember it moving freely when i moved it out of the way to replace the hood cable. i did remember seeing a post somewhere that someone blew compressed air into the motor (althought you arent able to open that aux motor) they said they also sprayed electrical cleaner in there and kept going and doing it over again...is this motor not repairable?
 

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It is not the motor that goes wrong but the computer block behind it that gets toast, but the two are not seperated.
 

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i already troubleshooted everything for the aux fan to kick on. everything is fine, that 50amp fuse was fine, the ecm to fan was fine, we used a snapon computer tool to manually turn it on and we used a power probe and multimeter to check for the hz. all of that checked out fine. coolant temp sensor on lower radiator hose is new too. outside temp sensor is new. anyway to fix the aux fan? or is it a must replace?
did the motor turn on when you tried controlling it with the snap on setup?
 

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That looks to me like the motor for the 3 speed relay and resistor controlled fan. I think you have the PWM fan with ~20 speed steps controlled by the DME, which is quite different.

The PWM motor has around 2 dozen small bus bars from the circuit board found in the motor assembly. In my case some of those bus bars had corroded and separated - no repair possible. Others though have reported failure in components on the circuit board, and these can sometimes be repaired - if one has the expertise. I recall seeing a DIY for the PWM fan circuit board several months ago; either here or the B-forums E39 forum. But I didn't save the link; you'll have to search.
 

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Mine might not be the same type as yours but mine wouldn't turn on when a/c button was pushed. It would turn once I turned the fan with my finger. I ended up taking it apart and re-greasing the fan parts/bearing. It's been a few months in 100deg heat and it's working great, but I suspect it's only a temporary fix. Removing the debris behind the condenser/radiator I think helped too.

http://www.bimmerfest.com/forums/showthread.php?t=902734&highlight=
 

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Look at the last pic in that post..inside the black area..the area that spins...I sprained bearing lube several times.
 

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But if you can't get the fan to spin but pushing (helping) it with your finger then my advice is probably not gonna help you.
 

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When I replaced my cooling system, the last thing i did was rebuild the main 3 wire fan connector which
was all corroded. Got new connectors from BMW. Soldered and shrink wrapped the male connectors on the
main fan plug and connected it to my new fan (Behr) female connector using some die-electric grease
on them for good measure.

Next was to check for any codes relating to the old electric fan failure or the failed coolant temperature
switch on the lower radiator hose which I replaced as well.

Using a Snap-On Solus, I found a code relating to the lower radiator hose temperature switch. To
clear this code,I disconnected the battery for ten(10) minutes and then reconnected the battery
and then using the Snap-On Solus I cleared the code. Since you have access to that Snap-On
reader I suggest you also check for a temperature sensor code.

Fired up the car and turned my A/C on and new fan operated correctly. If you have a code like this
a every day code reader will not show it. This code needs to be removed before the 3 wire (PWM)
system will function correctly. Thats how i did it.

Put my front clip back on and it's been good for a year and a half. My cooling and a/c system
works like it should to this day.
 

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Awesomely helpful post, thanks bmw blue! :) Damn, that SnapOn Solas sounds great, but a little pricey.... :(
 

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Any way to fix auxiliary fan?

Yes, Snap-On Solus very pricey...It belonged to a shop that I took my 2000 528I to
when I bought it in the summer of 2011 after my 1994 SHO had enough of the Chicago
winters....What a great motor that Yamaha V-6 was. Anyways.. This shop close to me
was a good BMW shop until the Dad/owner died.

The son let me use the lifts in the shop to work on my car for next to ZERO...and,
I learned how to use his $10,000 dollar Snap-On Solus on my car.

Thats what I understand from the shop owners as to the original purchase price of that tool/reader...plus a yearly update cost....Pricey..!

Shop is gone/sold now but I learned a lot about my car.... he gave me some cool
BMW tools when he sold the place. I didn't ask how much he wanted for the Solus.
I regret that i didn't shoot a price at him for it.... really nice tool.

Thanks for all the help as I look to this board always as a guide to keep my
ride running right.....
 

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I wonder if PA Soft would allow you to perform similar diagnostics on the cooling system?
 
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