Recently, the blower fan of my E46 318ti compact stopped working. A search on the internet revealed a number of possible causes:
- Dashboard control unit
- Blower resistor (also known as FSR, final stage resistor)
- The blower motor itself
- A cable somewhere in between
I could quickly rule out 1. When hooking up the car to INPA, the BMW diagnostics software, I could see that different fan settings led to different voltage readings. I ruled out 3. by measuring the voltage at the blower motor. It is not easy to access, you’ll have to remove some parts in the engine bay to get there and even then it’s still a tight fit. I measured no voltage there, leading to the blower resistor being the most likely case. All fuses were Ok.
The blower resistor is mentioned a lot on the Internet as cause for erratic fan behaviour or total failure, as in my case. When getting a replacement, make sure to buy a quality part, as the cheap ones are known to die quickly. My original unit was by Behr, my replacement is by Febi Bilstein, Hella is also a quality brand. I followed the instructions in this video (there are English equivalents. I did not find it necessary to remove the radio and climate control unit for removal and installation of the air duct. In total I spent about 45 minutes on this job, and it did indeed solve the problem as the blower is now working fine!
Since I was already ordering parts and noticed during the blower motor check that the interior filter was quite dirty, I also ordered a new interior filter and engine air filter. Changing the interior filter coudln’t be easier – turn the three retaining screws 90 degrees, remove the panel and the filter, place the new filter and put the panel back. The air filter is a different story. You need two unbolt the airbox, unplug or remove the air mass sensor, then remove the airbox and remove 7 screws that hold the lid. Assembly is in reverse order. It was certainly worth the effort if I compare the old filter to the new one.