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Thread: 850i Parasitic Leak causes dead battery

  1. #51
    Join Date
    Nov 2012
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    Little Rock, Ar, USA
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    My Cars
    '98 M3 '79 635csi '74cs
    Update:still stuck...
    I bought another GM (that's the 3rd). Still no luck. I think i keep buying bad units available from Ebay.
    Anybody could try my GMs and RMs on a good setup to confirm they are fine?
    If not i'll have to get the car shipped to Memphis to the nearest BMW place. But at this point I'd like to avoid any further expense.
    Thanks in advance!

    Quote Originally Posted by aeronotix View Post
    Nice - glad I'm inspiring!
    I had an aftermarket alarm correctly wired to the unlock/lock pins of the RM, removed it just in case. Otherwise aftermarket radio and I put back a CD43 on the original radio disconnect.

  2. #52
    Join Date
    Mar 2011
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    E31/32/34 VWJetta A3TDI
    Quote Originally Posted by aeronotix View Post
    HI,
    To understand if I have a localized issue on the GM/RM/relays and not the rest of the car I prepared a test bench outside of the car including the GM/RM/K70/K73/K15/K30/interior light relays. Both the GM and spare one I got on eBay are still not going asleep (.33A). See Excel snapshot attachments, the highlighted pins are wired. The test bench works exactly like in the car: I installed 2 lights to simulate the trunk light with the switch and interior lights. Trunk light never goes out and interior works good (if I momentarily ground pin 6 or 7 on X332 to simulate door opening, interior light turn on for 10s. Should I wire anything else on the GM/RM to make it complete so it goes asleep?
    I also prepared the attached pdf to recap pin assignment wire colors and function for helping others in similar trouble..

    Anybody would be kind enough to test them on a good functioning car?
    I don't of course pay for shipping both ways and more for the time spent.
    Bon weekend!
    Tonight, after receiving a module back from a member that still didn't work once installed, I decided to finally setup my test/bench setup, starting with a very minimal setup, i.e. with just the GM, an LED(+resistor) to represent the interior light relay, an LED for other output testing, and a few inputs. The general module draws about 50mA when powered by itself, with no loads attached. On it's own, the two I tested don't actually seem to power down below 50mA, and mine were fluctuating by about 10mA. (I tested with 2 different modules, same observation)

    I too observed the interior light relay coming on with grounding the door-pin input, though mine didn't stay on 10 seconds without door modules present, might be a difference in model year.
    Wondering if the 'wipers' were trying to reach home, I grounded X253-6 "Wipers to reset position" and X253-14 "wipers to park", no effect.
    Probing x254-2,3,4 (interface to RM) two were solid looking outputs and one was fluctuating every second or so.
    Without a relay module present to 'measure' the feedback current, I couldn't see the power protection relay signals ever engage(x254-24,25), and grounding the RM feedback and current detect inputs didn't change anything. My suspicion is that it's analog and the GM decides if the current is too high to allow the relay to turn on.

    Moving forward, I'm going to try my modules-under-test in my car, and verify what combinations of missing outputs the module still behaves properly.. (i.e. If I remove my door module, will the GM still behave properly, namely still going to sleep after 16min?)

    My suspicion is that the select few "GM still doesn't work after capacitor replacement" failures we've seen have something to do with another misbehaving module in the car.

    I'm also curious what kinds of random things the GM/my car will do when powered up in strange configurations (windows down, wipers not at home, etc)

    '94 525i, '89 735i, '91 850i, '81 MB 380SLC (For Sale), '00 323i -- Trying to collect them all, just need a 1 & 6

  3. #53
    Join Date
    Mar 2011
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    E31/32/34 VWJetta A3TDI
    Quote Originally Posted by aeronotix View Post
    HI,
    To understand if I have a localized issue on the GM/RM/relays and not the rest of the car I prepared a test bench outside of the car including the GM/RM/K70/K73/K15/K30/interior light relays. Both the GM and spare one I got on eBay are still not going asleep (.33A). See Excel snapshot attachments, the highlighted pins are wired. The test bench works exactly like in the car: I installed 2 lights to simulate the trunk light with the switch and interior lights. Trunk light never goes out and interior works good (if I momentarily ground pin 6 or 7 on X332 to simulate door opening, interior light turn on for 10s. Should I wire anything else on the GM/RM to make it complete so it goes asleep?
    I also prepared the attached pdf to recap pin assignment wire colors and function for helping others in similar trouble..
    So I've confirmed tonight that a general module will not go to sleep if powered up without the 3 wiper relays...

    I repaired a GM for Ed and had my car partially disassembled, so I dropped it in for testing..
    Battery disconnected, Connect module, reconnect battery. Current goes up to about 1.5A while IHKA initializes for about 10 sec. Unlock, Open, Close Lock door, current drops down to about 450mA in my car (With the Trunk lid button pressed momentarily. My EKM is currently disconnected too, so 450mA is a little lower than the norm pre-sleep current of about 500mA). ~20 minutes later I returned to find my trunk light still on.. Thinking "Oh crap-- another dud" I remembered my wipers were mid-wipe and my wiper relays removed.. Reinstalling the wiper relays, they moved slightly.

    I disconnected the battery and repeated my re-lock.. 16 minutes later, the current dropped down to 30mA (29.7mA when I switched ranges-- Note: this is still 10-15mA lower than usual because my EKM is not connected. Also note, the Antitheft LED probably draws 10-15mA too, which is 1/3 of the sleep current load!!)

    SO YES! MISSING (Or bad) WIPER RELAYS CAN IMPACT THE GM's ABILITY TO SLEEP!!!

    Also note, my wipers didn't actually go home, I had them in a mid-wipe position for testing.. The car went to sleep with the wipers in a partial wipe position anyway, so the wiper motor at home input doesn't seem too critical. (Unless it's just counting the rotations of the wiper motor gearing.?!).

    We're one step closer to creating a bench test!

    Other observations:
    The trunk lid button (that controls the trunk lights) doesn't seem to impact waking the car.
    However, the trunk handle microswitch will wake the car.

    When locking the car with the trunk and hood open, the anti-theft LED blinked a bunch of times indicating the car wasn't secure yet. (As Expected)
    Closing the open hood on an already sleeping car didn't wake up the car or trip the alarm.

    The key in the doors can wake the car, as will the door handle microswitches (even if still locked). I'm not sure the exact timing of a car going back to sleep if someone simply grabs the locked door handle to check if it's open, but I suspect it's still a 16 minute reset.

    My car has a misbehaving door module.. Locking and Unlocking the car a few times, there are times where the key in the driver's door doesn't always arm (or disarm) the alarm. I'm fortunate enough to have a passenger key lock, (removed in later models), so walking over and unlocking passenger door is another way to disarm the alarm.

    Tomorrow, I'm going to disable the alarm LED to see just how much of the remaining 30mA it's responsible for!
    30mA.jpg
    Last edited by EEDegreeToDrive; 07-19-2017 at 10:32 PM.

    '94 525i, '89 735i, '91 850i, '81 MB 380SLC (For Sale), '00 323i -- Trying to collect them all, just need a 1 & 6

  4. #54
    Join Date
    Jun 2011
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    NY, NY
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    84 633, 91 M5, 91 850
    Nice find. I'm going to re-check that the wipers are working correctly on my car. Any way to verify those relays are good besides just replacing?

    I'm also going to try pulling the door module on my car this weekend, but since my car doesn't sleep as it is I don't know that it will be a helpful data point (unless it fixes it, of course).

  5. #55
    Join Date
    Jun 2009
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    Canada
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    95 BMW 850
    I left my car parked for 2 weeks in wiper up position because I had to remove some debris from the wipers. The car went to sleep.

  6. #56
    Join Date
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    99 840ci Sport Indv
    The relays supply the 0V connection for the motor - without them the inputs (13, 14 and 25) to the GM will all be high and I doubt if the GM likes that!
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  7. #57
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    E31/32/34 VWJetta A3TDI
    Quote Originally Posted by Timm View Post
    The relays supply the 0V connection for the motor - without them the inputs (13, 14 and 25) to the GM will all be high and I doubt if the GM likes that!
    Yes, that's what I was trying to say..

    wipers.png
    Without the relays, wiper motor is 'floating'. However, the GM monitors all 3 legs of the motor, lets call them 'common', 'low', & 'high'. You need to energize common and either low or high speed to make the motor move... polarity determines direction
    Relay 3 selects the speed leg (low or high), while the polarity of the selected leg is chosen by relay 2 (+12V or 0V).
    Relay 1 selects the polarity of the common leg (0V or 12V).

    At any given point, at least one should be grounded. However, I've discovered that the GM seems to have a firmware bug that it can't continue when it sees all 3 inputs high (an implausible/transitional state, which is the case when the relays are removed, as all 3 inputs are floating).
    Normally, with all 3 wiper relays present, but de-energized, input 14 (motor common) should be 0V, Input 13 should be 0V, and input 25 should be floating.

    Note, most of the GM inputs float up to +12V or +5V and are then pulled to ground by switches, etc. Another interesting thing about this 'trend' is that current through microswitches and door pins is very low, probably pulled up to 5V or 12V with 10K resistors, so likely less than 1mA per activated input. This could make aftermarket equipment upset and certain aftermarket equipment (remote starts, alarms, etc) could also cause cause problems if the ETM isn't consulted first.

    - - - Updated - - -

    Quote Originally Posted by David9999999 View Post
    Nice find. I'm going to re-check that the wipers are working correctly on my car. Any way to verify those relays are good besides just replacing?

    I'm also going to try pulling the door module on my car this weekend, but since my car doesn't sleep as it is I don't know that it will be a helpful data point (unless it fixes it, of course).
    David, if you want, you can send one or more of your modules back to me and I can test them in my car.. If you're real lucky, aeronotix and I will have figured out enough to get a working bench test going!
    Last edited by EEDegreeToDrive; 07-20-2017 at 05:34 PM.

    '94 525i, '89 735i, '91 850i, '81 MB 380SLC (For Sale), '00 323i -- Trying to collect them all, just need a 1 & 6

  8. #58
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    84 633, 91 M5, 91 850
    Thanks for the offer! My first suspicion is still the GM, I am wondering now if it's possible the software is having issues. I'll have access to the car this evening and will check the wipers.

  9. #59
    Join Date
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    Quote Originally Posted by David9999999 View Post
    Thanks for the offer! My first suspicion is still the GM, I am wondering now if it's possible the software is having issues. I'll have access to the car this evening and will check the wipers.
    I did a whole evening of testing the other day on the things that wake the car, the things that will/won't prevent the car from sleeping, etc.. I'll start a new thread when my findings are complete!
    Regardless, I think my next parts order will include a few serial EEPROMs just in case they are borked..
    Last edited by EEDegreeToDrive; 07-21-2017 at 11:33 PM.

    '94 525i, '89 735i, '91 850i, '81 MB 380SLC (For Sale), '00 323i -- Trying to collect them all, just need a 1 & 6

  10. #60
    radlaw's Avatar
    radlaw is online now SoCalEights Member BMW CCA Member
    Join Date
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    Please refer to:https://www.bimmerforums.com/forum/s...-Battery-Drain

    Quote Originally Posted by revtor View Post
    ...[H]ave a closer look at relay K72 - it may be sticky. Pull K72 and measure resistance between pins 30 and 87a.

    If the relay isn't sticky don't re-insert it. Then measure the voltage over pins 4 and 8 of the socket where K72 was seated in.
    1) Did not find 87a; found 87b on K72 relay.
    2) Did above test on 87a & b. No resistance on either.
    3) Checked voltage between pins 4 & 8. None.

    Does this imply the both A1 (General Module) & A5 (Relay Module) are OK?

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