A common fault with E30s is that the heater blower often only works on the highest setting. You should be happy that it works at all because it is much easier to repair/replace the resistor that controls the speed, than it is to replace the entire blower. This project isn’t very complicated. Give yourself about an hour to complete it. As usual, these instructions are provided for your entertainment only. Use at your own risk: No wagering.
You’ll need some electrical contact cleaner, 6mm and 9mm sockets, phillips screwdriver, and a varied assortment of socket extensions for this project. You may need to also replace some zip ties as well. If you’re an optimist, you can hope all you’ll need is to clean the resistor once you get to it. If you’re a pessimist, go ahead and buy the resistor before you start. You can get it at your BMW parts counter or from Bavarian Autosport.
First off, double check that your blower still works on the highest setting, then disconnect the battery.
The panel you’ll need to remove first is at the back of the engine compartment. Remove the gasket that runs along the top. You’ll have to remove 4 bolts to free up the panel. The top two are easily visible, but the lower two are hard to get to. If you have a strut bar like I do, you’ll want to remove the wire bundle that is attached to this panel so you have some room to maneuver. That involves removing two screws and possibly removing some zip ties.
Once the first panel is removed, you’ll see the blower in the middle. There are two white straps holding on the blower cover. You’ll need to carefully open these and remove the panel by sliding it down and pulling it out. Be careful not to break the cover or the tie straps. Now you’ll see the exposed blower.
At the bottom of the blower, in the middle is the resistor module. Yours will probably be brown and quite dirty. In the photo you see the new light blue replacement. Remove the module by gently pulling it from the arms that extend down. Pull directly toward you. With the module removed, clean the electrical contacts on the blower. Be careful not to drip contact cleaner down into the heater. (At this point, if you were to reconnect the power, your blower would still work on the highest setting. If you want to test that, be careful not to damage the exposed fins of the blower. Remember to disconnect the power when you are done.)
You can either attempt to clean and replace your existing module, or simply plug in the new one. I tried to clean mine first, but ended up buying a new one when that didn’t work. Make sure the model is seated and reconnect the power. Then test if it works.
Reverse your steps by first replacing the blower cover and reconnecting the tie straps. Be careful working the top of the cover in first, then slide down into place.
Replace the outer cover and put the gasket back in place. Replace your wire bundle if you moved it and replace any zip ties you cut.
Enjoy multi-speed ventilation again.