2001 540i AUXILIARY COOLING FAN DOES NOT TURN ON WITH A/C

[Orxan4ik]

great great info guys, this board members deliver as usual! since we're on the subject I will clarify details for the future folks reading this thread.

Couple of days ago car doors were frozen shut on my car (-10F outside) I was able to get inside thru the back door and after starting the car I blasted the heat to defrost the locks somewhat. Trick worked and after about 30-40 minutes of idling I walked outside and caught needle in RED with KTEMP reading 133C. I was lucky to walk outside at the right time and shut her off immediately. After 5 mins of cooling I restarted @ 122C (still above AVE) and took off which dropped the KTEMP back to NORMAL rather quick.

FF >> 4 days and today I sat in traffic for about 10-15 mins (outside temp 45F) and the temp needle started creeping up. I shut her down, then restart once the traffic got going and everything once again was back to normal. I pulled over, turned AC ON and went to check the aux fan - it wasnt running.

At this point I think something is def up with the fan, rather than cooling flow. I need to at least verify the thing spins when forced to.


Q, it looks as if my fan doesnt do part 2 of stage 1 - kick on after 91F KTEMP. Fan is the first 1 I will check for sure!


I dont have much faith in replacement parts TBH, even though I always buy OEM. Somehow they just fail more often than original parts used to

[shortedaman]

Its not gonna run at _10.

[rf900rkw]

The info Q posted (thanks Q!) shows the IHKA turning on the stage 1 speed only at 50F and above.

- - - Updated - - -

Isn't the FC engaged by the temp via WP shaft?

Not behr, but a quick synopsis on how a thermal clutch fan works by a company that makes them.

Hayden Clutch Fan

[Flounderasu]

Not behr, but a quick synopsis on how a thermal clutch fan works by a company that makes them.
Hayden Clutch Fan

Thank you fine sir!

[mynameisjonas]

I just posted a new thread in hopes to find some help with a problematic 2001 740i overheating problem. The synopsis is that I have a new AUX fan that works when I put 12V to it, but not when it is plugged into the harness and when I test the harness for power there is none. Any help would be greatly appreciated!

Orig post: 2001 740i E38 - New Aux Fan has no power at harness, but runs fine with 12 volts.

I have a 2001 740i that has been giving me overheating problems for months. I have tried just about everything to resolve the problem and just when I think I have it figured out (replaced temp sensor 6 mo ago, aux fan 1 week ago and new fanclutch today), I discover the AUX fan I just replaced (1 week ago) is no longer working. I tested the fan by putting 12 volts to it and it powers up fine. The fan runs for a couple of seconds and then stops. I am guessing it stops due to there not being a signal for the resistor. I then checked to see if I have 12 volts at the Aux fan harness, and I have nothing. From what I can tell all of the fuses are good, as there are other accessories on those circuits that are working. I understand that there is another 50 amp fuse and two relays somewhere that might be the cause. I have dug through the treads and can't find anything with similar symptoms that included a fix.
Can anyone help and point me in the right direction?

Overview
New Aux Fan installed 1 week ago
Aux fan not working when plugged into harness
Aux fan works when 12V put to it
Harness does not appear to have power
New temp sensor approx. 6 months ago
New fan clutch today for water pump fan

[vien]

not to bring back old thread but im having a similar issue now on my 540

[ninetyseven1]

mine is a 97 540i, my question is: Does the engine have to be at a certain temp before the DME will energize the low speed aux fan relay?? I have replaced fan resistors, check ALL fuses even big fuse 75, replaced low speed relay. I can jumper the relay socket pins 87 and 30 and the fan works on the lowest speed like it should, but it doesnt work with the relay in! I can jumper the temp switch connector near the radiator and the high speed works. Can someone please shed some light here?

[Qsilver7]

mine is a 97 540i, my question is: Does the engine have to be at a certain temp before the DME will energize the low speed aux fan relay?? I have replaced fan resistors, check ALL fuses even big fuse 75, replaced low speed relay. I can jumper the relay socket pins 87 and 30 and the fan works on the lowest speed like it should, but it doesnt work with the relay in! I can jumper the temp switch connector near the radiator and the high speed works. Can someone please shed some light here?

Your 97 e39 has the 3 stage aux fan (not the variable speed aux fan that operates by a PWM signal from the DME). See "STAGE 1" in the quote below of post #25 (from the 1st page of this thread) that explains how the 3 stage aux fan operates for low speed (1st stage) for the 1996-1998 (e38/e39) BMWs with the M62 engine. Have you checked the dual temp switch?

Just an FYI to correct some of the info in the older portion of this thread.

The OP had a 2001 540i which would have had the M62TU engine, which used a variable speed aux fan. That fan doesn't necessarily turn on when the AC button is initiated. The variable speed fan turns on when it is sent a PWM (pulse width modulated) signal by the DME/ECU.

The 3-spd aux fan used in the 1996-1998 M62 (e38 & e39) does turn on when you initiate the AC:

The 1999 model year debuted the new variable speed aux fan:

[ninetyseven1]

Have you checked the dual temp switch?[/QUOTE]


Thank you for posting that btw. yes , i tested the dual temp switch with a paperclip and only the high speed comes on. The low speed of the fan only works when i remove the stage 1 relay and jumper terminals 87 and 30. I think im getting closer. I do have voltage at fuse 7 too. Someone mentioned if i test terminal 86 at the relay for voltage and if i get none then i may be a bad wire between the fuse and relay? so IF I DO get voltage at 86 then it may be a bad wire from relay to fan motor? does that sound correct?

[ninetyseven1]

Speed1.png

Have you checked the dual temp switch?

My gut is telling me the issue is more than likely in the red circles there on my attachment. Also maybe dual temp switch is bad Cause even when the temp hits 104 the fan wont go on high, i have to jumper the wires on the dual temp sensor to make the high come on.

[ninetyseven1]

maybe i can install the relay and ground the wire that goes to terminal 85 and see if the fan works ?

[rbelton]

If you're searching and arrive here for aux fan DIY, here's a video I just made detailing the removal and installation. Applies to pretty much all E39 models, the really early models are slightly different. Hope it helps someone...



link: https://youtu.be/CazRTB9J0uw