For anyone that has a blower motor that only works on high speed you may have a faulty resistor pack. The following is how I replaced mine.
64-11-8-391-749 - all E36 3-Series
64-11-1-381-784 - all E28 5-Series
The resistor pack is located just to the right of gas pedal of left hand drive vehicles. In order to get to the pack, you must remove the pedal cover.
Two screws hold on the pedal cover. One is located just under the headlight controls; in the photo I had already removed the screw.
The other screw is under the dash to the right of the steering column, again the screw is already moved in the photo.
Once the screws are removed there are two clips holding the cover on. One is on the far left of the dash..
The other is just right of the steering column
Pull to the rear of the car and the cover will remove easily.
Disconnect the plugs on the chime speaker and remove the cover.
Now you can see the pack back of the pack. Unlatch the small clip holding it in housing and pull out.
Remove the electrical connection and you are ready to replace the pack. Notice the rusted area on the bottom coil. This was the reason mine was not working; the rust lost the continuity of the connection.