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Discussion Starter · #1 ·
On my '04 330i, I've been on high-alert over the years for battery drain on the blower-motor resistor. I've been through a couple of battery-drain episodes, but it was never this part - so mine is still original.

I've never had trouble with the blower - aside from a squeaking noise at low speeds. This morning, the blower wouldn't come on at all - on manual, on Auto, etc... I left it on about 2/3's speed - and headed to work. As I hit some rumble divots in the highway a few miles out of town, the blower came on and ran normally.


So my question is - does that sound more like a loose wire? Or could it be the resistor beginning to fail?? What is the normal mode of failure for the resistor? Will the blower motor itself fail like that? Or is it likely in the power control wiring?
 

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So my question is - does that sound more like a loose wire? Or could it be the resistor beginning to fail?? What is the normal mode of failure for the resistor? Will the blower motor itself fail like that? Or is it likely in the power control wiring?
The FSR is more of a transistor motor speed control than a resistor. It sounds like you have loose wire connection.
A bad FSR can cause fan not running, or running when it was turned off, or run at low speed regardless of the speed control setting.
 

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I had the same signs as you, I believe the cause is in the brushes and commutator wear. If you hit hard on the top windshield vents on the dash, chances are the blower will start spinning. I bought a used blower motor and compared the wear, huge difference. Swapped it out and it works.

Follow this tutorial, it's not a hard job, just a PITA.
 

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If the blower motor resistor is original I would replace that first since its a known issue. Even if it turns out to be the blower motor you would have to replace the FSR anyway. Correct?
So tackle the easiest known defect first before the big one.
Report back
 

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'03 325iT Mystic Blau
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This describes exactly the way that my blower motor failed, except I did have any noise warning of things getting bad.
Sometimes when it wouldn't run it'd start after going over a bump, once I figured that out I was able to get it started several times with a "technical tap" on the dash, but replacing the motor fixed it.
 

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Discussion Starter · #9 ·
Thanks for all the advice!!

I’d been thinking about replacing the motor, anyway, because the “cricket chirp” at low speeds has been getting increasingly annoying.
 
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