ventilation fan does not work

[M6 Dream]

I am an owner of M6'87 since a few months. I have a problem with ventilation. In case AirCondition is on then cold air is properly distributed via front and back ventilation system. I am able to adjust smoothly fans [both] speed. In case air con is off then ventilation is not working at all. What can be a reason of such situation. Fall time is commin now and I have no heating in the car?

[sharkfan]

The AC uses a fan underneath the stereo aperture and the normal ventilation uses a fan under the black ribbed plate at the back of the engine bay near the bottom of the windscreen.

The fact your AC works means the problem is with ventilation fan under the bonnet.

If you have temperature control issues there is an electronically controlled thermostatic water valve on the inlet side of the engine bay screwed to the same bulkhead that the ribbed metal plate is screwed into.

Hope this helps.

[M6 Dream]

Thanks for that, don't you know if there is any fuse or braker to check first prior to verification of Fan itself. I have no user manual. I recall that diring the first drive it worked properly , then it started to work full speed with no possibility to adjust the speed of the fan. When I started the engine next time ventilation fan was dead.

[sharkfan]

If it was only working at full speed for a time before complete failure I would first replace the transistor that controls the fan speed; for the ventilation fan in the engine bay there are (should be) six posidrive screws holding the ribbing cover on. Undo these then ease the cover off, next carefully un-clip the rounded fan shields off and remove them and you will find the fan and the transistor that controls the fan speed; part number 15

http://www.realoem.com/bmw/enUS/showpar ... Id=64_0464

The BMW part number is 64111381784 but if you're confident with a soldering iron and willing to do a search on here you might find a radio shack/maplins part to solder in; I did and they work very well.

Good luck