Auxiliary fan appears dead - simple diagnostics - 2006 3.0 - Page 3

fiataccompli · #1 08-10-2016, 01:24 PM

Quote:

Originally Posted by dkl

but I know it isn't dead because it does kick on when the car is hot. Most days it stays on for about 5 minutes even after shutting down the car. Does this means my AUX fan is only half functional?

THIS is what gets me confused because it appears that the fan is operating to assist (a pusher fan...makes sense, right?) the main radiator fan. Guess i'm just thinking out loud at this point because I know two parts that are about to replaced on our X5...

dkl · #2 08-10-2016, 11:02 PM

Quote:

Originally Posted by dkl

Thanks for the DIY video. My AUX fan doesn't run when I turn on the AC (only the main fan spins and AC is working as expected), but I know it isn't dead because it does kick on when the car is hot. Most days it stays on for a few minutes even after shutting down the car. Does this means my AUX fan is only half functional?

I'll run a scan tonight to see if there's a fault code for the AUX fan.

Just scanned the car (using BMW Scanner 1.4) - no fault code for the AUX fan. Doing a realtime scan on the AC unit and all functional. So now I'm baffled as my AUX fan don't come on with the AC as some of you guys have indicated that it should but I don't have any faults on my system

The AUX fan does run when the radiator is hot enough, just not when turning on the AC.

fiataccompli · #3 08-10-2016, 11:28 AM

Since I rarely drive the car, I was relying on my wife's description. According to her, these recent issues all began when without warning the expansion tank blew up dramatically and it overheated (and she parked & rented a car). She said she had not noticed any AC issues until after the tank (and the thermostat that sits in the bottom
Of it ) was replaced. It overheated again (also, immediately grounded) and I thought it was my own fault due to inadequate "burping" of the coolant...but with that checked & double checked & no apparent external or internal coolant loss but another overheat today, clearly I need to check other stuff and the thermostat is the first stop.

I did actually drive the car a good bit over the last week to try to put it through its paces, basically trying to bring it to a failure point if it were to reach one, but it seems my wife had the special touch on this one!

upallnight · #4 08-11-2016, 07:20 AM

The aux fan comes on when the high side pressure sensor indicates to the DME that the high side pressure is rising. The fact that you don't have a fan fault after a scan and the fan does come on when the engine temp is hot means the fan is fine.

You could be low on refrigerant. To determine this you will need to connect a set of manifold AC gauges to the system and read the low and high side readings and note the ambient temperture.

dkl · #5 08-11-2016, 11:28 AM

Quote:

Originally Posted by upallnight

The aux fan comes on when the high side pressure sensor indicates to the DME that the high side pressure is rising. The fact that you don't have a fan fault after a scan and the fan does come on when the engine temp is hot means the fan is fine.

You could be low on refrigerant. To determine this you will need to connect a set of manifold AC gauges to the system and read the low and high side readings and note the ambient temperture.

Appreciates the inputs and clarifications

jsoto · #6 08-11-2016, 08:09 AM

Just for clarity or the wiki, I recall the aux fax was supposed to turn on for a few secs. on startup just to tell the DME was good, but as well, I was under the impression the aux fan literally engages once AC was on

upallnight · #7 08-11-2016, 08:26 AM

Quote:

Originally Posted by jsoto

Just for clarity or the wiki, I recall the aux fax was supposed to turn on for a few secs. on startup just to tell the DME was good, but as well, I was under the impression the aux fan literally engages once AC was on

The DME does spin the aux fan at start up, but the aux fan does not come on the minute you turn on the ac. For example, if you were driving on a highway, the air passing through the condenser is enough to cool the refrigerant in the condenser so the aux fan will not come on. It is only when there is not enough air passing through the condenser that the aux fan will come on.

fiataccompli · #8 08-13-2016, 04:06 PM

as promised, I'm updating. Originally, I thought I'd end up a bit delayed in replacing the fan, but another overheat (upthread) along with a decent amount of OK feedback on one of the non BEHR fans pushed the decision to go ahead & replace the fan. Did it yesterday (timed to be waiting as UPS walked up with the new TYC fan) with a bit of consultation of a couple youtube videos the verify the loosening of the front bumper (of which I was not believing at first). Anyway, it appears to have completely returned the AC to proper function to freeze you out of the car and we now have a day of normal use (I told my wife to put it through it's paces but keep an eye on the temp) so far. I'd heard some comments about noise of the TYC and that is a non-issue on this one (maybe the engine is loud, maybe the old fan -OEM, btw - had bad bearings the last I heard it). Fit was as the OEM and the job itself if rather easy...actually super-easy, just tedious.

I also got a thermostat, but decided to be a bit more scientific since I had no scan indication of a thermostat problem...it was simply one of those things that is probably a good idea & without the fan having failed, I would have suspected a periodically sticking thermostat as the culprit. I guess the fan is for the next rainy day.

I've heard some comments about these fans failing & burning the car. As long as there is no human injury & it's not parked to close to one of my Fiats, that would not be a terrible thing as the X5 is insured and we are comfortably "right side up" in our investment....though, I'd prefer it simply continue to be a good car for the family - whether that continues to be my wife, or we give it to my daughter.

oh, the scanner was a little glitchy in installation. I gather that the instructions regarding WHEN to attach the scanner & when to attach it to your car need to be followed closely. I had a brief period of Windows XP (SP3) (gotta love the old junker laptop!) hanging up even when I had pointed it to the correct driver. I think I ended up loading a driver from a link in Bimmerforums (and there was also a nice software link to dropbox, but I did not end up needing it), but it ultimately installed correctly and was able to read everything. I did, in fact, have a fan fault (no blown fuse, by the way).

Thanks all of you for your feedback/directions/time on this one. I hope the thread proves helpful to someone else.

Qsilver7 · #9 08-14-2016, 11:39 AM

Just an FYI for those that questioned why their aux fan didn't come on when the AC was initiated...as already mentioned by others...since the debut of the M52TU, M54, & M62TU engines, the aux fan has been the "variable speed" type...and unlike earlier engines used in the M62 & M52 engines (prior to 9/98)...the aux fan doesn't turn on immediately when the AC button is pressed.

The 2-speed & 3-speed aux fans used in the e38 & e39 between 1995-9/98 did turn on when the AC button was initiated...but the variable speed aux fan waits until a PWM signal is sent from the DME/ECU after certain criteria is met (along with a quick aux fan check at start-up):