Aux Fan oddity ..need help.

[PalmSpringsE534.6]

Ok everyone...here goes. DME set a fan error. Aux Fan not turning on with INPA. Slow to cool as Aux Fan not running....and darn near overheated with AC on and sitting in a traffic jam.

Had my shop replace the fan. Still inoperative. AC compressor is cycling on and I get cooling as long as I'm moving (as expected).

Checked voltage at fan connector. Getting proper voltage on the hot...and the ground is good. Getting approx 2v on the signal wire. I don't have a scope to check the wave form.

If I recall properly, if I pull the plug on the AC pressure switch the fan should run up to full speed in a few seconds...right?

If not, any suggestions on what to check next?

[andrewwynn]

Definitely confirm fan will spin. Do you have scanner/software that will engage the fan? That's the best way to confirm.

If you are seeing voltage on control pin see if you can read duty cycle or Hz and you can help determine if the fan is getting the proper signal.

New ≠ fixed. You have to test the new fan to make sure it actually works.

In the meantime when my aux fan wasn't working and it was 90F out I used my scanner to kick on the AC compressor periodically to keep the cabin cool.

[sandbagger]

$5 says its a dead fan... EBAY
Also you dont have to pull the bumper beam, but you will have to do some light prying/bending.... but it will go. yes the bumper cover will have to come off though.

[andrewwynn]

I removed mine upwards I had to remove a few things on top of the radiator.

[Effduration]

Yeah what fan did the shop use?? I would hate to think even an aftermarket new fan would not work out of the box, but stranger things have happened.

I just went thru this.. My aux fan wasn't working, but had good power and ground. I tried activating it with INPA, but it would not spin. I got my other X5's fan to spin using INPA.

I tested my replacement fan with INPA before installing. Just plug it in and lay it on top of the radiator.

A new Genuine BMW fan is $600 and OEM Mahle/Behr is $475. Both were a little steep for me.

Based on good reviews, I bought the TYC (Taiwan) fan with lifetime warranty for $160.
So far its working fine.

https://www.amazon.com/dp/B00DY68XMY...ing=UTF8&psc=1

[oldskewel]

Originally Posted by Effduration

Yeah what fan did the shop use?? I would hate to think even an aftermarket new fan would not work out of the box, but stranger things have happened.

I just went thru this.. My aux fan wasn't working, but had good power and ground. I tried activating it with INPA, but it would not spin. I got my other X5's fan to spin using INPA.

I tested my replacement fan with INPA before installing. Just plug it in and lay it on top of the radiator.

A new Genuine BMW fan is $600 and OEM Mahle/Behr is $475. Both were a little steep for me.

Based on good reviews, I bought the TYC (Taiwan) fan with lifetime warranty for $160.
So far its working fine.

https://www.amazon.com/dp/B00DY68XMY...ing=UTF8&psc=1

Good info on that replacement. I might end up going that route too.

On the earlier question about not having a scope to test the signal wire, I posted a bunch of detailed info in another thread on here about how to test the fan and the fan control.

But briefly (and from memory, so this could be wrong but that other thread is right), I was able to measure the effective duty cycle on that signal wire using my humble True RMS voltmeter. I believe it is a ~12V, 1 Hz, square wave coming from the ECU, with the duty cycle (on-vs-off duration of the square wave) changing as the ECU wants to command a faster or slower spin rate. The motor controller is in a circuit board right on the back of the fan motor on my 3.0i (and I believe all gas engine E53s, different for others, where the controller is in a box in-line with the power and signal cord).

And one important thing, if you try to measure that signal with a True RMS voltmeter - I think I found I needed to have the 3P fan connector plugged in to make it work. So for example, if you had the fan disconnected, and tried to just probe the signal wire, it would not give you anything.

So if you do all that and find the ECU is putting out a varying voltage (you'd see the integrated voltage vary from about 1V to about 11V as the commanded speed changed), that would be a good indication that your fan is bad. But if you don't see a valid signal on the signal wire, it could mean either the ECU is not working, or it could mean that the ECU detected a problem with the fan and is not sending a command.

[X5chemist]

My fan failed three months ago. Looking for a replacement, my one requirement was a brushless unit if available. A TOPAZ 64546921381 fit the bill. One year unlimited mileage use. Through Amazon, you can add a four year replacement plan. It's a good deal.
After turning off the X5, the fan spins down for 10-12 seconds. Turns on with A/C control. I'm not sure sure about DME control. I have yet to test it. When I have time, I'll try to use my Foxwell 520 Pro.

[andrewwynn]

Fox will run the fan. If it runs at all the DME is doing its job.

Mine failed where it passed the start test but didn't run to cool the condenser so I only had quality ac when moving. I never used to hear the fan running but now any time I have ac on I hear the fan when in front of the car.