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Thread: Battery drain due to passenger mirror circuit. How to troubleshoot?

  1. #1
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    1998 BMW 740 iL, January

    Battery drain due to passenger mirror circuit. How to troubleshoot?

    Passenger mirror circuit on Fuse 8 ( right front door module : passenger window / passenger lock / passenger mirror ) is preventing vehicle from going to sleep.
    Without mirror circuit ( unplugged connector x1130 at passenger right front door module A24 ) the car will sleep after 16 minutes and draw 0.04 Amps.

    With mirror circuit connected, battery drain of 0.64 Amps after 20 minute wait. Guess that is No Sleep condition.

    The passenger mirror circuit has 8 wires.
    I am in the process of trying to understand what color wire controls what function and also which wires act as a feed and return leg to each functional circuit.
    Do not understand why there are more than 4 wires as does General Motors Chevrolet Suburban mirror which I have dissected.

    Can anyone enlighten me as to what I might suspect as culprit of drain?
    Is the passenger side mirror heater in the same circuit?
    It appears that the heater may have its own dedicated wire that runs separate from the 8 bundled wire set. Not sure of that.

    Open to suggestions regarding how to proceed .
    Hoping that I do not have to purchase a BMW passenger side mirror.
    What goes wrong in this circuit?
    Is it a mirror motor or heater draw?

    When dealer diagnosed that right front door module was faulty, I replaced it.
    That did not solve the battery drain issue.
    I looked downstream of the right front door module and found eliminating the mirror circuit would stop the battery drain.
    Ideas?
    Last edited by Stilllearning6; 11-06-2016 at 02:19 PM. Reason: Typo : x1130 ( correct) vs x1131(incorrect)

  2. #2
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    600mA sounds like the mirror heating element - but it could also be (as you say) something else demanding current as the car has not gone to low-current mode. I would remove the mirror glass and disconnect the heater to start with:

    http://www.meeknet.co.uk/E38/Mirror/Index.htm

    ....if that makes no difference disconnect the motors/potentiometers in the mirror. The mirrors have servomotors and these require power and give feedback via potentiometers, hence the load of wires!

    However, this sounds more like something is holding the P bus active and that is not allowing the car to go into sleep mode.

    More info below:

    Mirror functions

    The mirror functions include electric mirror adjustment, mirror heating, mirror memory (option) and electric mirror fold-in (option).
    Mirror adjustment

    The mirrors are adjusted electrically by means of the peripheral modules for the driver's and passenger's doors. The adjustment switch is located in the central switch block on the driver's door.
    Switch operation is transferred via the P-bus from the switch block to the peripheral module in the door. The door module drives the adjustment motors in the mirrors by means of semiconductor bridges.
    Electric motors are installed in the mirror housing for horizontal and vertical adjustment.
    Mirror Memory

    If the vehicle is equipped with a seat/steering column memory the mirror positions are registered and stored accordingly.
    The seat/steering column memory features its own peripheral module (its own diagnosis program) which is linked via the P-bus to the general module of the ZKE. The positions for the seat and steering column are registered and stored in this peripheral module.
    Parallel to this, the mirror positions are stored in the peripheral modules of the doors (door modules).
    The mirror positions are detected by means of potentiometers which are installed on the mirror drive.
    Memory mode is operated by means of the memory switch which is linked by four lines to the peripheral module for the driver's door. Button operation is transferred via the P-bus to the general module.
    The mirror, seat and steering column positions are stored as of terminal R. After pressing, the red memory button lights for max. 7 seconds. If one of the memory buttons (1, 2 or 3) is pressed during this time, the current positions are stored in the selected memory slot.
    A stored position can be called up at any time. The function is, however, deactivated 16 minutes after switching off the ignition until terminal R is switched on again or until a signal change takes place at a module input (e.g. opening a door).
    The positions are called up by pressing the required memory button (1, 2 or 3) until all adjustment have been carried out. In addition, it is possible to start an automatic operating sequence by briefly striking the button. This ”single-strike mode” is possible when:

    • The driver's door is open and ignition lock is in position 0
    • The ignition lock is in position 1 (terminal R ON only)

    Mirror Heating

    Mirror heating is controlled by the peripheral modules in the doors. The heating function is active as of terminal 15 (ignition lock position 2). The activation time is dependent on the outside temperature.
    The general module receives the outside temperature from the IKE via the K-bus and determines a cycle time for heating operation. This time is transferred to the peripheral modules where it is carried out. Heating is no longer active at an outside temperature greater than 25 oC and it is switched on permanently at a temperature lower than -10 oC.
    Folding In Mirrors

    The electric motor drive is used to fold in the outside mirrors (special option) in the opposite direction of driving.
    The button to fold in the mirrors is located in the switch block on the driver's door. The button signal is routed via the P-bus to the peripheral modules in the doors. Depending on the position of the mirrors, they are then folded in or out accordingly.


    In addition to the external design differences, the mirrors for the production vehicles model E38/E39 from the mirrors for the model E39 M5 (motorsports design).
    A microswitch is integrated in the mirrors the production vehicles that switches a ground signal to the relevant peripheral module when a mirror is folded in or out by hand or by impact. The microswitch is necessary as folding the mirror in or out uncouples the mirror mechanism from the fold-in motor. If a mirror which has been mechanically uncoupled is activated by the button being pressed, the fold-in motor will move the mirror in the fold-in direction until the microswitch registers the mirror being engaged. The maximum activation time of the motor is 15 seconds.


    Thanks to a modified mirror mechanism, this microswitch is no longer necessary for the mirror of the E39 M5.
    Since the mirror fold-in motors block when operated, thermal overloading is possible if operated frequently. In order to avoid overloading, a repeat lockout is provided which blocks the fold-in motors for 3 minutes after 6 operating attempts within 1 minute.
    Last edited by Timm; 11-05-2016 at 04:59 PM.
    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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  3. #3
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    I agree with your thinking about removing the heater circuit to eliminate the heater circuit as a battery drain suspect.

    I did not know how to eliminate the circuit, nor did I have a clue about the secret process to remove the heated mirror.
    Thank you for the link.

    If the 0.64 Amp battery drain goes away when the mirror heater circuit is removed, I am not sure if the fault resides in the exterior heated mirror or upstream of the heated mirror at RFDM (A24) or General Module3. Why will car not go to sleep after 16 minutes? Perhaps fault in GM3 (in the mirror circuit of GM3?).

    Note:
    RFDM was replaced when dealer dx was drain in RFDM. A used replacement RFDM did not resolve the battery drain.
    I am leaning toward not suspecting my original OEM door module, nor do I suspect replacement door module.
    Yes, I could have 2 faulty RFD modules, though too much coincidence in my mind.

    I disconnected the 3 connectors at RFDM ( A24) and drain stopped.
    As mentioned earlier, only by adding mirror circuit connector x1130 did drain appear.
    Not sure if the draining circuit needs to make a round trip to its end component (some component in heated mirror?) to make battery drain appear.
    Have not ohm tested any of the mirror circuit due to difficulty in access and lacking wiring understanding. Still studying circuit.

    I tried to access the upstream door hinge connector x256 by removing the 8mm hex head screw in door hinge connector plastic boot cover.
    I could not readily get to the connector , even though I pulled it out of its living space within the car frame door pillar. Did not disconnect it.

    I am intrigued by the dedicated black wire which appears to lead to the passenger mirror.
    See photo below.
    It looks to be 2 wires enclosed in a black sleeve.
    It is separate from the 8 wire bundle that originates at right front door module(A24) .

    I am hoping that this dedicated wire has something to do with the heater circuit .
    If yes, then it may be easier to unplug this dedicated wiring rather risk playing in the exterior heated mirror circuit wiring.
    I am timid about dissecting the delicate exterior glass heated mirror.

    Can you comment on the dedicated wire ?
    Can you provide assurance that the exterior glass mirror is sturdy enough to withstand my tinkering?
    If the 0.64 drain has ceased with the x1130 connector unplugged, I may sit this one out for awhile.
    I am thrilled to have stopped the battery drain.

    I respect / admire your knowledge base and experience.BMW mirror heater wires?.jpgBMW mirror heater wires?.jpg
    Last edited by Stilllearning6; 11-06-2016 at 02:16 PM. Reason: Typo : x1130 ( correct) vs 1131 ( incorrect)

  4. #4
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    The black wire is the window pinch strip.

    To stop the heater circuit, remove the mirror glass and pull one or both of the heater contacts off.
    See my E38 parts for sale on eBay: click here!
    PM me here for a 5% discount on any of them!

  5. #5
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    Got it . Thank you.

  6. #6
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    After 2 days of having unplugged the passenger side mirror electrical connector x1130 at the right front door module --> no battery drain issues.

    This forum has advised me to disconnect the electric heater wires at the passenger mirror to isolate the mirror heating circuit from the rest of the mirror functions to help identify the cause of my battery drain due to failure to enter sleep mode.
    Sounds logical.
    I have not done that yet as I am concerned for damage to passenger side mirror by me. I can envision snapping plastic parts.

    In the meantime, I am pondering what can possibly happen in the mirror heating circuit to cause the car not to sleep.
    Should the mirror heater circuit be eliminated via logical thought?

    I am speculating that the mirror heating circuit is merely : current IN --> heating element resistor wire --> current OUT via return leg.
    As I see it, either the circuit is incomplete ( due to corrosion / broken wire ) or it accidentally gets a ground somewhere.

    I do not recognize how either of those 2 choices would be associated with a "failure to sleep" condition of drawing 0.64 Amps after the 16 minute wait.
    During my test conditions, my vehicle draws 0.64 Amps while waiting the 16 minutes , then drops to 0.04 when it sleeps.
    Sounds acceptable.

    I understand how an incomplete circuit would lead to a zero amp draw.
    I understand how an accidental short to ground would lead to a massive draw.
    I do not understand the reason that a heated mirror circuit fault would produce a " does not go to sleep " condition.

    Can someone educate me?
    I certainly understand the concept of disconnecting the heater mirror wiring as an isolating step.
    But, is it rational?

    If the heater circuit were not faulty, what other passenger mirror circuits would precipitate a failure to sleep condition?
    Is it a memory position issue?
    Is it a vertical or horizontal motor issue?

    Based upon studying Timm's above post of the mirror functions, I am pondering whether the driver side mirror control switch, which directs power /adjustment instructions to the passenger side mirror, has a role in the battery drain.
    I would hope that when the switch that controls either driver side mirror vs. passenger side mirror is selected to choose driver side only, then the passenger side motor circuits should be inactive/dead.

    Perhaps the mirror memory circuit over-rides the manual driver mirror switch button??
    If the memory circuit were faulty, the memory circuit might be continuously sending signal to the passenger mirror (??).

    I am leaning more toward the fault lies with memory circuit , not heater circuit.
    Yet, I have not heard any passenger mirror motors humming. I could have missed that clue.

    I am a novice at this , so kindly consider my ignorance of the subject and be gentle on me.

    I appreciate your feedback and educational lessons.
    Hoping to reason out the source of the fault.

    Update:
    The Fold-in mirror" option was not installed in the vehicle.
    Perhaps a fault in that circuit anyway??
    Last edited by Stilllearning6; 11-08-2016 at 10:11 AM. Reason: Additional data

  7. #7
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    Disconnecting the wires to the mirror heater was not put forward as a fix - just a stage in diagnosis!
    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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  8. #8
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    Yes, just to help isolate one of the many circuits of the mirror.
    After I posted , I wondered how that would be interpreted.

    If the drain goes away with the heater mirror circuit disconnected while the remaining circuits were functionally connected, I would still have to figure out where in the entire heater mirror circuit the fault might reside. It might be outside the mirror, I imagine.
    Not sure how many components that would involve.

  9. #9
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    Did you find this fault?

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  10. #10
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    No. I have not gotten back to this issue as daily life consumed my free time fix-it past time.
    Perhaps I will revisit again this fall as weather is acceptable.
    I removed the Fuse 8 two years ago to eliminate the drain.
    I lack window control, door lock, door courtesy light since Fuse 8 is removed.
    I forgot about this posting and the depth that was explored.

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