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DIY: Do It Yourself
Post here to share or improve your wrench turning skills! All BMW E46 DIY tips, tales, and projects discussed inside. Learn to work on your car and know the right BMW parts you will need!

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Old 07-20-2011, 05:35 PM   #1
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Location: Belle Plaine, MN
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My Ride: 01 325 CI
Troubleshooting: Final stage resistor or blower motor

The blower motor isn't working. I have the rheostat style HVAC controls and have tested the blower motor on all 4 speeds, with and without the AC and with recirculate.

I know the FSR is a common issue, but I'm not one to throw parts at a car unless I know I have isolated the broken part. My logic, check to see if the blower motor has power, if it does we know a fuse isn't bad and (I would assume) the FSR is working. I don't have a load tester but am assuming speed is regulated through amperage. This isn't defined in the Bentley manual.

When the car is off, zero voltage (as expected) is at the blower motor. When the car is on and the fan is set to any speed I get 12v on each pole of the electric motor (confusing). Leave the car on with the fan turned off, I still get 12 volts (even more confusing).

Short of unhooking the motor and connecting a 12 volt source to see if it spins, how would I continue to verify that it is the blower motor and not the FSR? Or is there another way to isolate the FSR/blower motor that I haven't found yet on the forum?

Last edited by Spyder_Venom; 07-20-2011 at 05:36 PM.
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Old 07-20-2011, 06:05 PM   #2
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So for those of you that plan to test it - here is the deal.

You can't take the voltage on the poles of the motor. You must remove the plug from the pass through in the blower motor cage. The driver's side pin will be fed 12 volts (constant) and the passenger side will have a variable voltage. The voltage should be (based on my car):

Fan speed 1: 4v, fan speed 2: 2.5v, fan speed 3: 1, fan speed 4: 0v.

Time for a blower motor.
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Old 07-20-2011, 06:08 PM   #3
Zero. Leaks.
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Do you have zero air flow or pulsing air flow?
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Old 07-20-2011, 08:56 PM   #4
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I had zero air flow when the car was stopped. There is a secondary blower motor that you can feel at speed located mounted down by the steering column. I was working on the primary blower motor located behind the cabin filter. The air flow I had while in motion was not enough to keep the cabin cool today (90F +).
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