as stated in title my 89 IX power door lock stoppped working after car sat outside long enough for battery to go nearly flat i tried unlocking doors and heard locks cycle multiple time due to weak battery, i didnt jump start it instead i disconnected battery and charged it , reconnected it and found power locks stopped working , just spent some time on my issue today before the rain starts , first check voltage at both sides of fuse #27 (central lock main fuse) it was ok ,next pulled door jamb connector apart figuring if the deadbolt lock inhibit grounding was my issue once that was disconnected locks would work at other doors ,no change , also checked that pin in the connector for short to ground and it was fine ,even cycled door lock with key and it changed from grounded to open ok so i know that the deadbolt switch is operating properly. next checked Unlock/Lock signal wires from drivers door lock switch at the jamb connector signals again were ok . well now it onto the central lock control module in drivers kick-panel, removed and check power at red/blk OK check ground Brn continuity ok , cycled drivers door lock with key (being sure to hold module vertical at all times) and heard relays click in both lock and unlock position , well thats wierd i thought why am i not hearing door lock actuators operating , cant have all gone bad at the same time , so i alternately jumper power and ground to the white and blue lock motor control wires right at the module connector (module disconnected of course) and lock motors try to operate that tells me wiring is ok and motors are ok but it wouldnt open , then i remembered the last time i locked the vehicle before batt went dead i deadbolted it , so i had to jumper power to the black deadbolt motor control wire and well as ground to blue wire and heard pass side deadbolt release , back to jumpering power/ground to blue and white and now lock motors function ok . so problem has to be inside module . take module inside and remove top and sure enough the internal fuse has blown (just a soldered bi-metallic strip ,will get this resoldered on monday at work and have locks again. at times when batteries go down the door locks can cycle repeatedly to the point of blowing this safety fuse (which BMW considers unrepairable,and there is a TSB about and updated module i think) ,but its an easy fix so just a FYI for future reference.
attached are pic's of control unit disassembled with screwdriver tip pointed at offending blown bi-metallic fuse (it should be bent over and touching top of resistor with solder). i installed control unit without the cover and manually held strip over to contact point and door locks now work
its about a $100 control module so worth fixing ,part #61311380302
attached are pic's of control unit disassembled with screwdriver tip pointed at offending blown bi-metallic fuse (it should be bent over and touching top of resistor with solder). i installed control unit without the cover and manually held strip over to contact point and door locks now work
its about a $100 control module so worth fixing ,part #61311380302
Attached Files