E36 M3 A/C won’t blow over half speed... Usually.

[TranceE36]

Battery is new and provides correct voltage. A/C system USUALLY doesn’t increase fan speed past speed 5 of the total 8 speeds. Very rarely, speeds 6-8 will work. Speeds 1-5 always work fine. A/C blows cold. Just replaced cabin filter, which I didn’t expect to fix the issue, and of course it didn’t.

Any idea what the issue could be? My blower motor was being a bit squeaky at low speeds last year, so maybe that’s the problem. Could also be the Final Stage Unit? Any help is appreciated. Sorry if this has been addressed. I searched and didn’t find an answer.

[JDStrickland]

Final Stage Resistor.

There's always the chance that the fan motor is gooey and dirty and simply won't go fast anymore. There's no way to know that from my side of the keyboard. I drove my E36 for something close to 20 years and NEVER turned the fan off. To be honest, I cannot remember the last time any of my cars was driven with the fan off. Never ever turn the fan off, that's my approach to life.

[Eric93se]

You can actually repair the FSU. Under the black tar stuff are soldered connections that crack, remove the old solder and put fresh. I have an old pic but can't attach it now.

[GutterHelmet]

I had a similar issue, this fixed mine.

[Eric93se]

I eventually got an aftermarket FSU off ebay and while it looked OEM it worked a bit differently, the lowest speed was much higher than an OEM unit. This at first was a little annoying but i n the long run its a much better design. The OEM unit will run hot and eventually fail when run at the lowest speed because the fSU relies on that air flow to cool it down.

Here is the one that came with my car that I repaired and it worked a while longer but eventually something else inside failed.

[shogun]

Moved to E36 M3 forum from E36 forum

[WBS]

Final Stage Resistor.

There's always the chance that the fan motor is gooey and dirty and simply won't go fast anymore. There's no way to know that from my side of the keyboard. I drove my E36 for something close to 20 years and NEVER turned the fan off. To be honest, I cannot remember the last time any of my cars was driven with the fan off. Never ever turn the fan off, that's my approach to life.

I did not even know the fan could be turned off. Yes. I never turn my fan off either.