My HVAC blower motor may be a casualty of sub-zero temps (UPDATED)

When it’s cold out, the auto climate control on my 335xi waits to start blowing until the engine has started warming up, even when it’s “on.” This is a nice feature to prevent being blasted with freezing air when starting a cold ass car.

My wife and I alternate weeks of who gets to use our 1-car garage. She has it this week. This morning it was -4° F. I started my car, let it warm up a little bit, and headed to work. About 2/3 of the way through my 8 mile commute, I noticed the heat still hadn’t started blowing. Normally it only takes a few minutes before the engine has warmed up and the heat starts blowing. I tried switching the climate control over to manual mode, but nothing happened. I continued on my way to work, thankful that at least my seat heaters were working.


Initially I thought it might just be the blower motor didn’t like being parked outside overnight in the cold-ass temps, and maybe if I put my car in the garage tonight and let it warm up, it would resurrect the blower motor.

But it’s been this cold all week and the blower worked fine until now. So I did a little research. According to this, it might just be a blown fuse, or it could be something called a final stage resistor, or it could be the blower motor. Replacing the blower motor isn’t too difficult, but maneuvering up and under my dashboard in my not very warm garage is pretty unappealing to me.

So I called my mechanic, and they have some time available to check the car out this afternoon. My wife and I were planning to meet for lunch today, so now we’re just going to meet at the mechanic first and then go to lunch. At least this probably will only cost a few hundred bucks at most to fix.


At lunch I went out to the car and tried turning the fan up to high and banging on the panel under the glove box as the mechanic suggested, but no response from the fan. So I brought it in to the shop. My lovely wife picked me up at the mechanic, we grabbed some falafel at the quick-serve Mediterranean joint by my office, she dropped me off at work, and I just got a call from the mechanic.


He was able to get the motor to blow, eventually, but there were some electrical burn marks on the final stage resistor. He tested the motor with the oscilloscope and the signals from it were all smooth indicating no likely mechanical fault in the motor itself. He has a resistor in stock and he’s popping it in. Total damage is $285 and I can pick the car up later today.


This is a solution I will live with.

Also, falafel is good.

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