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Thread: E46 Blower Motor not working

  1. #1
    Join Date
    Jul 2013
    Location
    Calgary, Alberta, Canada
    Posts
    117
    My Cars
    94 540iT, 04 325i,

    E46 Blower Motor not working

    Hey all,

    I have a 2002 325i. Recently the blower motor was initially intermittently working, and now has stopped working completely over the course of a week. I replaced the motor (it was squeaking and was a good excuse to finally change it). Im getting the IHKA module working fine, the module is increasing the voltage as I turn the fan speed up (determined with a live data feed on my code reader). I've checked the fuses in the glove box, and swapped another relay in to eliminate that is the cause (I put the original relay back in). I checked to see if I have power going into the relay, I wasn't getting power on the "30" pin on the relay (from wiring diagram it looks like this is the main power pin?), but I do have power coming in on the 85 and 87 pin on the relay. Am i right in thinking the relay and power to the relay is fine?

    the last thing now is the Final Stage Resistor (I think), Is there anyway to properly test the final stage resistor? I checked and I have power coming from the resistor harness.
    I tried grounding the resistor housing to metal glovebox mount to see if it was a wiring issue or a resistor issue, fan still not working. I checked part numbers and it seems its the same part number as the FSR in an E39, so I grabbed a resistor from the e39 I have sitting in the driveway and tried it as well, no dice still. the resistor in my E46 has a rectangular shape and the one from the E39 is triangular shaped. For diagnostic sake, does the difference in resistors mean the fans not working due to the difference in resistors and my resistor is bad or that its something else in the system? i checked rockauto and they have both styles listed for the e46.

    your help is much appreciated!!

    /I

  2. #2
    Join Date
    Apr 2016
    Location
    Philadelphia
    Posts
    175
    My Cars
    1997 m3
    Sounds like a Final stage resistor. I had an e46 final stage resistor go bad and with an aftermarket one the blower motor stayed on even if the car was off and key out of ignition. The blower motor would turn on or off when i would go over bumps lol. An oem one solved the issue.
    Check fuse 50 (40amp) in the glove box fuse box. That is directly tied to the final stage resistor. Also probe the blue/red wire going to the Final stage resistor, should be reading 12v with car on and blower on.

  3. #3
    Join Date
    Jul 2011
    Location
    Arlington, VA
    Posts
    9,933
    My Cars
    2018 BMW M240i
    I concur, the FSR is likely bad. Check the condition of the FSR’s wiring and connector when you pull the old one out. The wiring and the connector are subject to a lot of heat which, over the long term, damage them.

  4. #4
    Join Date
    Jan 2007
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    Should have replaced the FSU first! The FSU is 99.9% always the culprit. Especially when it's an intermittent issue.

    But, like you said, the blower motor was noisy anyway.
    ASE and BMW Master Certified Technician

  5. #5
    Join Date
    Jul 2013
    Location
    Calgary, Alberta, Canada
    Posts
    117
    My Cars
    94 540iT, 04 325i,
    Thanks for the input! I tried a new FSU and got no luck, tore everything apart, checked the power to the fuses, relay, into the FSU and then finally went to check power into the motor and found out the new motor that i had bought was faulty. the brushes were sparking against the contacts and the motor would spin up and then die, spark, spin up and die, etc... (confidence inspiring...). i put the old FSU and grabbed another motor from a parts e46 and everything is functioning normal.

    I'm still not sure why the initial intermittent issue started, however, for a few days it has been working completely normal. i have the extra FSU just in case things go south again. thanks for the help!!
    Last edited by Ilovemy525i; 10-13-2017 at 04:30 PM.

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