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Thread: E46 battery drain. SOLVED!!!

  1. #1
    Join Date
    May 2012
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    12

    E46 battery drain. SOLVED!!!

    I have an E46 2003 320i Msport. I thought I would share my experience as all the info I got from forums kept leaving me at a dead end with a dead battery. Turns out they were all right- FSR is usually the problem. Anyway, my battery kept draining within a week, if I parked up on Sunday the alarm would be sounding by Thursday/Friday or sometimes Saturday morning, if I used the car for a short trip in the week. I took it to a BMW specialist to get the FSR changed but by the end of the week the alarm was sounding again. I took it back and they tried the oil pressure sensor but it still did it. For the next 7 months I had to live with the hassle of disconnecting the negative battery terminal every time the car was laid up for the week. So I decided it was time for me to do some investigating of my own since the garage were unsure of what it could be. I bought a fuse adapter which fitted into a multimeter so I could measure the amp draw of each fuse in the fuse box in the glove compartment. I rolled the windows down and closed the doors then waited about 25 mins to make sure it went into sleep mode. (I noticed the park light on the gear selector went out when it did.) I found out that fuse 50 which is a 40A was drawing between 160 & 220 milliamperes. It kept climbing but I gave up when it hit 220. Also fuse 63 (7.5A) seemed to be drawing 90 milliamperes. If I left these two fuses out the drain stops but obviously the blower didn't work. With this I figured there was definitely a problem with the HVAC/air con, but as the FSR had already been replaced I had to assume it wasn't that. Next I pulled out the HVAC control unit which was easy, just use a flat screwdriver on either side and it pops out. On the back there are two white and one black connectors. I unplugged the black connector and checked the voltage on the back through each of the holes and one said 0.33v. The culprit was the blue/red wire. Upon checking the wiring diagram for the heater blower in the Haynes manual I realised that blue/red goes from the FSR to the HVAC control unit. So now I had my doubts about the FSR, and the only thing I could do was to have a look myself. I used a guide I found on the web and stripped it all down to get access to the FSR. Apart from some torx screws missing I yanked out the FSR to have a look; and guess what? It was a pattern part or an eBay special. I went down to my local BMW dealer and asked to view a genuine FSR and you could see the difference. So after having to pay out for the new hedgehog I went back and fitted it, reassembled the car and have had no problems since. So if your having the battery drain problem I'd advise to check fuse 50 for a high milliamp draw and also check the voltage on the red/blue behind the HVAC (I got 0.33v which dropped considerably after fitting the new FSR) So my advice would be - don't buy a hedgehog from eBay! Get an official one from BM.

  2. #2
    Join Date
    May 2002
    Location
    NWA
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    5,802
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    2006 330i
    Interesting, not the first time I've heard of a pos aftermarket FSR causing problems.

    Reminds me.. I need to pick up a multimeter. Had my eyes on a certain Fluke for some time now.
    Last edited by WoLF; 07-27-2013 at 01:58 PM.

  3. #3
    Join Date
    May 2012
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    12
    That's what I used. Can't go wrong with a fluke!

  4. #4
    Join Date
    Sep 2008
    Location
    alabama
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    5,537
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    2002 bmw 325
    Fluke is the only meter I will use.

    Op glad you got it figured out. I have seen more fsr causing issues than I care to even think about.
    02 BMW 325
    13 MB GLK350
    94 GMC sonoma 4x4 - hpd30/8.8 - toy
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    GOIN BROKE BUT N STYLE

  5. #5
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    Mar 2005
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    ( ͡ ͜ʖ*)
    Can you break that into paragraphs to make it easier to read?

  6. #6
    Join Date
    Apr 2012
    Location
    Golden Horseshoe, Ontario
    Posts
    399
    My Cars
    e36 - 1998 323is
    What is FRS?

  7. #7
    Join Date
    Jul 2011
    Location
    Arlington, VA
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    9,770
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    2018 BMW M240i
    Quote Originally Posted by mr ilia View Post
    What is FRS?
    Final stage resistor. It's part of a circuit that controls the speed of the heating and air conditioning fan. It's a common failure in E46's. Easy to replace and not too expensive.

  8. #8
    Join Date
    May 2012
    Posts
    12
    Hi, shortened version as requested.


    I have an E46 2003 320i Msport.

    I took it to a BMW specialist to get the FSR changed but by the end of the week the alarm was sounding again. I took it back and they tried the oil pressure sensor but it still did it.

    I rolled the windows down and closed the doors then waited about 25 mins to make sure it went into sleep mode. (I noticed the park light on the gear selector went out when it did.)
    I found out that fuse 50 which is a 40A was drawing between 160 & 220 milliamperes. It kept climbing but I gave up when it hit 220.

    Also fuse 63 (7.5A) seemed to be drawing 90 milliamperes. If I left these two fuses out the drain stops but obviously the blower didn't work.

    With this I figured there was definitely a problem with the HVAC/air con, but as the FSR had already been replaced I had to assume it wasn't that.

    Next I pulled out the HVAC control unit. On the back there are two white and one black connectors.
    I unplugged the black connector and checked the voltage on the back through each of the holes and one said 0.33v. The culprit was the blue/red wire. Upon checking the wiring diagram for the heater blower in the Haynes manual I realised that blue/red goes from the FSR to the HVAC control unit.

    I used a guide I found on the web and stripped it all down to get access to the FSR. Apart from some torx screws missing I yanked out the FSR to have a look; and guess what? It was a pattern part or an eBay special.

    I went down to my local BMW dealer and asked to view a genuine FSR and you could see the difference.
    So after having to pay out for the new hedgehog I went back and fitted it; had no problems since.

    So if your having the battery drain problem I'd advise to check fuse 50 for a high milliamp draw and also check the voltage on the red/blue behind the HVAC (I got 0.33v which dropped considerably after fitting the new FSR)
    So my advice would be - don't buy a hedgehog from eBay! Get an official one from BM.

  9. #9
    Join Date
    Nov 2013
    Location
    Nottingham, England
    Posts
    2
    My Cars
    2003 320d Sport
    Hi guys i'm having very similar issues and would like your advice please.
    After reading this thread i was convinced i would be buying a new hedgehog! However i have completed the tests above and now i'm not so sure! current draw tests on fuses 50 and 63 (plus any others listed to do with HVAC) all check out ok and voltage at blue/red was only 0.16v. Is there anything else i could test to check the hedgehog in otherways?.

    Searching other threads has lead me to look at the electric flow heater ( name taken from real OEM- other people seem to call it auxiliary water heater) I disconnected the thick black earth lead and got a reading of 0.22amps (ignition off) so i am thinking its not good that this unit is drawing current and could be source of my problem. However i would have expected to see current draw at one of the fuses but can not determine which fuse this unit uses. to confuse me more there also seems to be an auxiliary water pump ( sits in front of heater) and i wonder whether this could be at fault. A ny help or advise would be very much appreciated.

  10. #10
    Join Date
    May 2012
    Posts
    12
    Update,
    It might not be the FSR. I can hear a faint noise coming from the HVAC control unit which I'm assuming is the mini fan that draws cabin air in, to pass over the sensor.
    I hear this when the car is in sleep mode. After unplugging the big white clip from the back every night the battery doesn't drain at all, even when left for a week.
    Questions is, why is it constantly on. HVAC faulty or something else???

  11. #11
    Join Date
    Sep 2006
    Location
    Michigan
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    13,674
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    2005 325Xi
    Quote Originally Posted by spoonerDee View Post
    Can you break that into paragraphs to make it easier to read?
    Was going to +1 this comment because tl:dr but I thought it'd be fun to Cliff the OP:

    My repair didn't fix anything.

    I thought it was the FSR, but it wasn't.

    I'm still working on it.

    I'll let you know.
    Quote Originally Posted by B4SH View Post
    If anyone knows, it's this guy who knows literally nothing about everything.
    Quote Originally Posted by fcvapor05 View Post
    Do you even OT? The mean 401k around here is probably about $6, what with all the shiny cars and $1,000 watches and donations to get other members' Volvos running.


  12. #12
    Join Date
    Mar 2005
    Location
    Connecticut
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    ( ͡ ͜ʖ*)
    It could be the climate control unit itself. They are supposed to stay on for a short time after the car is turned off to continue cycling hair or something to that matter. For whatever reason, yours doesn't want to turn off.

    Question, does the drain still happen if you turn the climate control off then turn the car off?

  13. #13
    Join Date
    May 2012
    Posts
    12
    No matter what I do, it'll drain unless I unplug the CC unit. Been unplugging it for months now and it hasn't drained since. Need to source a new climate unit and see if that solves it.

  14. #14
    Join Date
    May 2017
    Location
    Glasgow
    Posts
    1
    My Cars
    F31 320ed E46 320cd
    Hi Chris, did you get to the bottom of this please? Thanks

  15. #15
    Join Date
    Mar 2017
    Location
    Norwich, Connecticut.
    Posts
    486
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    E46 wag. E36 convertible
    After reading these posts...my question is WHY is any dc activity present...after switching OFF the ignition switch....(a battery kill switch lives in the marine and government for all their assets) as is so, on most, if not all cars imported to the USA!....................... Is this the a connection to 'mysterious' WORLD-WIDE BMW fires occurring 2017...BMW is not talking!

  16. #16
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    Sep 2012
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    El Paso Del Norte, TX, US
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    ‘15 F31d Msport
    Quote Originally Posted by Eaglesail View Post
    After reading these posts...my question is WHY is any dc activity present...after switching OFF the ignition switch....(a battery kill switch lives in the marine and government for all their assets) as is so, on most, if not all cars imported to the USA!....................... Is this the a connection to 'mysterious' WORLD-WIDE BMW fires occurring 2017...BMW is not talking!
    can you write coherent sentences and post coherent questions?
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