Get a Bentley before you do anything..

I've got the same problem with an 82 528e..

I actually think BMW did the right thing not integrating HVAC..  if one goes
down, they don't both go down..

Quick check.. does the fan work at ANY setting?  you can usually rule out
the resistor pack if the fan is working only at the highest setting.

You may have eithe a faulty switch, a bad fan motor, a bad ground, or a
loose connection.  Hence the excelllent previous suggestion of checking for
voltage.  If you don't have or know how to use a multimeter, now's a good
time to learn, or pony up the 50 bucks for the half hour labor at the shop
to run a voltage check.

IF its the fan motor.. I'd suggest hitting Vinesauto.com, Bimmerparts.com,
or any one of the wholesalers selling good reconditioned heater fans..
Install is quite simple.

Remove your firewall at front of the hood.. either hex bolts or phillips
head screws.. remove the plastic fan shroud by unclipping it at the tabs..
un hook the electrical connector in the middle of the fan, and pull it up as
a complete unit.  Drop in the replacement and re-attach the firewall, and
welcome back to the land of defrosted front windows!

here's to hoping that this crappy weather in the Northeast clears up long
enough so we can get under those hoods!

Good luck!

This is often just a bad connection to the motor, try cleaning it.