Aux Fan - 2001 e39 M5

[ortontom]

The initial message was deleted from this topic on 17 July 2010 at 08:30

[Hedgetrimmer]

ortontom said:

Either somethings wrong or im mad.....the aux fan doesnt seem to come on at the mo, it did last year - not had any temp issues, kept a close eye on it.

Any suggestions where to start looking

Have a look at your settings within the "Computer" menu. The timer may have been reset to zero.

[ortontom]

no the cooling fan for the rad, not the climate control...

thanks anyway..

[M5 Cambridge]

They are prone to go bad. Start your car, hit the max cool AC button, then watch the fan for about 2mins, when they go bad, they judder every 30 secs or so as it trys to start. Also If you have a peak code reader it will show up as error 35 (aux fan relay). Not really fixable, time to change it I'm afraid.

Good luck

[CarbonBlackM5]

I think mine has gone too because with the aircon on the temperature rises when sitting in traffic. It doesnt do it when its off.

Is it an easy fix? Is it just a solenoid thats needed or a sensor too?

[Mroad]

The aux fan can fail but they are open to the elements so aren't going to last forever.
As posted above by M5 Cambridge check the aux fan is spinning with the air con on. With the engine off and the fan stopped also try spinning it by hand to feel for any resistance. If it doesn't spin freely it's buggered.

The aux fan is easy to check so check that first however it's worth checking the viscous fan especially if the water temperature is rising.
The viscous fan is the main cooling for the radiator, the aux fan is simply for the air con condenser and on some BMW's to help out the viscous fan if the water temperature rises too high.
The viscous fan may well appear to spin but it doesn't mean it's providing enough air flow if the viscous coupling has failed.
The old trick for testing it is with the engine warm is to try and slow and stop the fan with something that won't damage it or yourself (e.g. rolled up newspaper). If you can stop it fairly easily, it's buggered so not an ideal test if it's working OK.
Alternatively with the engine fully warmed up switch off then try spinning the stationary viscous fan. It should be very hard to spin by hand when hot, if it spins easily then it's buggered and time to replace the viscous coupling.

I've had both go on my E36 M3 which is basically the same system as on the E39 M5 (and most other BMW's).
I ditched the aux fan and the air con when it failed (it's a track car) and the viscous fan fault only appeared when it was sat at highish revs for the MOT, when on the road it was fine from natural air flow. I ditched the viscous fan and replaced it with an electric unit so it's only needed when required.

[CarbonBlackM5]

Right I have given it a try. The viscous fan spins all the time and increases its speed when I rev the car. I presume this is right. (When the engine is off the viscous fan is fairly hard to spin and doesn't spin freely)

As the water temp rises to over halfway the aux fan doesn't cut in or try and spin at all. I did check the fuses and it lists 4 but only two are present. Is this correct? If the aux fan is faulty is a complete replacement needed?

Edited by CarbonBlackM5 on Sunday 11th July 19:28

[CarbonBlackM5]

I have been doing some research on M5board and it sounds like the clutch on the aux fan has gone. It spins both ways with ease when done by hand with the engine off.