E30 Zone

Hi,

I've had the issue of settings 1 - 3 not turning on the blower fan, however 4 does at full speed, and 0 turns it off. I've been behind the firewall and taken the blower fan out, checking for resistance in the spinning, the carbon sticks, and spraying the entire motor encasing with brake cleaner and WD40 to no avail.

My partner and myself threw a multimeter on the end of the contacts to power the motor and on all settings it's getting +12 volts, so we assumed that the resistors were inside the motor housing, but both of us (I've been a mechanic for BMW for 4 years and he's an electrical engineer) can't see anything that could house resistors.

Any ideas on what could be causing the problem with the speed variation?

Not 100% sure but i think this is the resistor.
They usualy fail because of stiff or seized bearings in the blower.

Most people tend to stick it a vice work some grease (i used copper slip) into the bearings and hook it to power and it should help free them off.If it squeaks stick some more grease in.

It depends if your car is equipped with air con, If it is you will find the resistor pack just under the fan motor assembly, It has 3 wire coils on it of differing guage wire to vary the resistance and hence the fan speed. It is removed by simply pulling it out towards you. The fan works in pos 4 because it bypasses the resistor.
On non air con equipped cars i think the resistor is mounted in the fan assy enclosure in the left hand corner , it is accessed from behing the glovebox i think, this topic has been covered at length before and searching for "fan and resistor" should point you in the right direction.
this link may help if you have air con
http://e30.bmwdiy.info/blower-resistor/index.html