Pusher fan does not run

I have been reading for hours to try to diagnose my problem. The electric cooling fan is not coming on on my 2000 E39. Found the malfunction while working on AC problem. If i understand correctly, the ECM commands the fan to run, and what speed, using data from the temperature sensor on the lower radiator hose, and the pressure switch on the AC.

It should come on momentarily when the car is started, and any time the AC is turned on.

If the temperature sensor fails, would it keep the fan from coming on when the AC is turned on?

Would low AC pressure keep the fan from coming on?

I added some refridgerant with dye to locate the source of the leak in the AC. Guage readings at 100 ambient temperature are 70 low side and 270 high side.

Thanks in advance for any help. I have been unable to find a definate answer to either question.

It looks like the fan has gone south, you need to replace it. I replaced mine about a year ago. You'll need to remove the bumper, headlights and few other items but fairly easy diy job. The fan is about $350 though :/

Sent from my MB860 using Bimmer App

From what I understand, it should run anytime the A/C is on even if the engine is cold. A/C pressure being low would prevent it running.

FWIW, I tried to replace the coolant temp sensor in the radiator hose first to see if I got lucky and that's only what it was, but no dice for me. I got the cheap TYC fan since it was half of what the OEM unit costs and it's working fine so far. The job was much easier that I thought it was going to be. I would suggest having someone help you remove and reinstall the bumper cover. It's not heavy, but it has to be lined up perfectly. Just take your time and it's an easy job.

For anyone who was following this, I chased this problem for 10 months, and finally found a thread that talked about Dyanvin Radio interfering with the HVAC control. Reflashed the IBUS and Everything has worked flawlessly for about a week. I have had the fan blower motor stay on, replaced the Final Stage Unit, Pusher fan on condensor would not turn on. Replaced fan, and still wouldn't run. AC compressor would not turn on on. HVAC controler would not control blower fan, or temperature. Blower fan would speed up and slow down when shifting from park to drive and back. If you are having difficulties with HVAC, and have installed an aftermarket radio, search for Dynavin for possible solutions.

Wow. Good to know. Thanks for sharing. Who would think to trace a HVAC issue to an Dynavin install?!!

Good thing I've got the old resistor style, not PWM fan!

Originally Posted by cowboyjer

I have been reading for hours to try to diagnose my problem. The electric cooling fan is not coming on on my 2000 E39. Found the malfunction while working on AC problem. If i understand correctly, the ECM commands the fan to run, and what speed, using data from the temperature sensor on the lower radiator hose, and the pressure switch on the AC.

It should come on momentarily when the car is started, and any time the AC is turned on.

If the temperature sensor fails, would it keep the fan from coming on when the AC is turned on?

Would low AC pressure keep the fan from coming on?

I added some refridgerant with dye to locate the source of the leak in the AC. Guage readings at 100 ambient temperature are 70 low side and 270 high side.

Thanks in advance for any help. I have been unable to find a definate answer to either question.

The fan has two modes of operation. The low speed mode is controlled by the temp sensor on the radiator and A/C pressure switch. The high speed mode is purely a function of the temp sensor on the radiator. It is a fail safe mode to prevent the engine from overheating and under normal conditions, it augments the mechanical clutch fan on the engine under extremely hot conditions.

The best way to troubleshoot it is figure out which pins on the temp sensor are for high and low speed operation. It is a 3 wire sensor. Brown wire is ground. Other two pins are for high speed and low speed. Jumper each pin to ground separately. If fan comes on in high speed mode but does not turn on when you jumper the low speed pin, there is a high probability that the resistor mounted on the fan to drop voltage for low speed operation has burned out. This would be the least expensive repair. It is also possible that low A/C pressure would stop low speed fan circuit from working but high speed mode is not affected by A/C. If fan does not come on in either mode, fan is bad. This assumes you have checked fuses before doing this test and made sure none are blown.

The ac PSi switch is directly related to the fan relay (it is the input single)

2 things..

jump the pins together at the connector (on the harness) with ING 1 on @ the Ac Psi switch... does fan come on ?
fan comes on switch is bad
fan does NOT come on move to 2nd step

place known good ground at connector for fan
place 12v DC to connector directly to fan
does fan come on? yes move to diag relay
Fan does NOT come on ... replace fan

For what's its worth when you guys post Q&A'a about the aux fan it would be good to say which fan you are talking about.
The single speed fan that uses resistors, relays, the AC pressure switch, and a temp switch on the side of the radiator or the PWM fan that has no resistors/relays to control the fan speed.

Lil your crack me up bro , you certainly got the BMW forum down

There is only one aux fan

Originally Posted by Burning2nd

Lil your crack me up bro , you certainly got the BMW forum down

There is only one aux fan

Right, there is only one Aux fan, but there are two different types of Aux fans. They are not controlled the same way.