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Thread: General Module successful repair #2

  1. #26
    Join Date
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    1997 840ci
    Quote Originally Posted by dgoebel View Post
    Special thanks to ah1cobra for spurring me to finally do this. Same electrical issues: door locks, trunk, windows, interior lights, etc. didn't work in the morning if it was cold. Took it to dealer with general module information from this forum and they DENIED it was the general module. Half a dozen shop guys there said it was the relay module, which they replaced for $450 parts and claimed they tested for 4 days. By chance I picked up the car on the coldest day of this year in S.Cal. (frost on the roof) and nothing worked just like before. Drove the car home and everything worked by the time I hit the driveway. Ordered the capacitors on line from www.Newark.com for about $6 and they arrived two days later. Pulled the general module (my 1995 840ci has the cartridge holder under the left side of the dash and removing two nuts on the bottom edge allows it to swing down enough to get the modules out), replaced the capacitors and everything is working great. Photos in ah1cobra thread were very helpful.

    The five capacitors from BMW have axial leads and are rated at -40C to +85C.
    10 microFarads at 63 V
    1 microFarad at 63 V
    47 microFarads at 25 V
    100 microFarads at 25 V
    470 microfarads at 40 V

    I replaced them with capacitors rated at -40C to +125C and with a higher voltage rating for the lower ones. These were a little larger than the stock versions, but fit fine. Probably last forever now.
    10 microFarads at 63 V
    1 microFarad at 63 V
    47 microFarads at 50 V
    100 microFarads at 50 V
    470 microfarads at 50 V
    Thanks for the excellent info. I have the same issues with my 97 840ci. My question is: how do you know that it's the capacitors that are bad & not some other component on the control module? Did you have a scan run to determine the faulty components?
    Thanks again!
    jkr740ci

  2. #27
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    1996 840Ci / 2007 B7
    Quote Originally Posted by jkr840ci View Post
    Thanks for the excellent info. I have the same issues with my 97 840ci. My question is: how do you know that it's the capacitors that are bad & not some other component on the control module? Did you have a scan run to determine the faulty components?
    Thanks again!
    jkr740ci

    Mainly, I decided that as everyone claimed that replacing the capacitors fixed the exact same issues that I was having was good enough diagnostics for a $15 repair. It's not unusual for capacitors to go bad over time, so whomever figured it out first had a good prime candidate to start with. There are plenty of writeups - mine is here: http://forums.bimmerforums.com/forum....php?t=1786611

    Good luck!

  3. #28
    Join Date
    Nov 2011
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    Croatia
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    1992 BMW 850i 4spd
    My trunk lights, sun visor lights never work, and some other interior electronics occasionally malfunction. I know that the bulbs aren't blown because i checked for voltage on the bulb terminals.

    Would you guys blame the GM and do the replacement?

  4. #29
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    Scottsdale, Az
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    1997 840ci

    Thumbs down General Module

    Dgoebel,
    I've read your posting regarding the General Module. I have a 97 840ci which has demonstrated the same symtums as you noted. My question is do I need to have it scanned first to determine if it is the Gen. module or something else. Also, how do I know that it is the caps that have failed & not some other component on the board? Also I have been looking for any pictures or tech info on how to remove the unit & where to start.
    Any information you might be able to provide would be greatly appriciated.
    Thanks,
    JKR840ci

  5. #30
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    Made in Germany
    Quote Originally Posted by jkr840ci View Post
    how do you know that it's the capacitors that are bad & not some other component on the control module? Did you have a scan run to determine the faulty components?
    Because electrolytic capacitors have a limited life span and there's practically nothing else on the printed circuit board that can go bad under normal conditions. Aging, under-dimensioning and poor quality of electrolytic capacitors are the cause of failure in many devices...

    There's no point in reading error messages in this case. With bad capacitors the A1 general module (GM) no longer works reliably and the same goes for its diagnostic capabilities. Luckily the symptoms are easy to recognize: Wipers that act funny, windows that no longer drop when you open the doors, the trunk lock which cycles endlessly rapidly burning its coil, the central locking system that no longer works correctly, the interior lights that no longer automatically turn on when you open the doors, the consumer cut-off which no longer works draining the batteries while the car is parked,... If your car exhibits two or more of these symptoms, which often resolve themselves when the car heats up, you can be pretty sure the capacitors in the GM are the culprit.
    Also I have been looking for any pictures or tech info on how to remove the unit & where to start.
    Spandrel already gave you an excellent link (Success in General Module Repair) and there are plenty of other topics covering this repair...

    Quote Originally Posted by Ledo View Post
    My trunk lights, sun visor lights never work, and some other interior electronics occasionally malfunction.
    I don't know what "some other interior electronics" are, but the sun visor lights are not controlled by the A1 general module (GM). In the early cars you have to turn on the parking/headlights before the make-up mirror lights can work.

    The luggage compartment lights are controlled by the K72 consumer cut-off relay which on its turn is controlled by the A5 relay module (RM) and A1 general module (GM), but if K72 does not actuate for various reasons the interior lights and glovebox light would not work either.

  6. #31
    Join Date
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    1992 BMW 850i 4spd
    The luggage compartment lights are controlled by the K72 consumer cut-off relay which on its turn is controlled by the A5 relay module (RM) and A1 general module (GM), but if K72 does not actuate for various reasons the interior lights and glovebox light would not work either.
    Thanks for the reply,
    my interior lights work when the doors are opened, but can't be turned off or permanently on at the switch like they are supposed to be The glovebox lights work, but the trunk lights never come on, and i find it very frustrating.
    I was hoping that my problems were due to a couple of faulty capacitors, but someone obviously tampered with the wires

  7. #32
    Join Date
    Mar 2011
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    Damascus, Maryland USA
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    E31/32/34 VWJetta A3TDI
    Quote Originally Posted by Ledo View Post
    Thanks for the reply,
    my interior lights work when the doors are opened, but can't be turned off or permanently on at the switch like they are supposed to be The glovebox lights work, but the trunk lights never come on, and i find it very frustrating.
    I was hoping that my problems were due to a couple of faulty capacitors, but someone obviously tampered with the wires
    Interior Lights: --Bad dome light switch - pretty common
    Trunk Lights: --Bad trunkpin switch, or blown fuse

  8. #33
    Join Date
    Jan 2012
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    Queen Creek, AZ
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    1991 850i, 2007 X5.
    Quote Originally Posted by dgoebel View Post
    Glad to post the Newark Part numbers and some hints on the replacement procedure.

    www.newark.com
    Aluminum Electrolytic Capacitors, Axial
    Newark Part Numbers:
    #97C7972, 10 microFarads at 63 V, $1.14 each
    #14M8286, 1 microFarad at 63 V, $0.852 each
    #97M4027, 47 microFarads at 50 V, $0.163 each
    #75K6216, 100 microFarads at 50 V, $0.182 each
    #79R7674 470 microfarads at 50 V, $0.832 each

    Plus shipping. As I said before, they're a little larger than the stock ones, but fit in fine. There's lots of room away from the board and you just place the four that go together side by side.

    Remove the old capacitors by placing a hot, tinned soldering iron on one of the capacitor leads AND the pad below and use a pair of needlenose pliers close to the capacitor body to pull the lead out of the board. Pressure on the pad keeps you from ripping the solder pad off the board while you pull the capacitor lead out. If your iron is hot enough and you make good contact with the lead and pad, it doesn't take much force to pull out the lead. Repeat for the other lead to remove the capacitor. I then used a vacuum desoldering tool from Radio Shack to get the residual solder out of the hole (heat the pad with the soldering iron and then suck out the liquid solder). You can use solder wick too, which is copper braid that you just press against the hole with the iron on the back to melt the solder and wick it out. Then bend the axial leads sideways on the capacitor, slip them in the two holes (being careful to get the polarity right), resolder by heating each lead and the pad while you apply the solder, and then trim the excess lead off on the back side. Be sure to check that you made the solder flow down the lead so that it also wets the pad on the backside of the board. You can apply a little solder to the back side to fill it in if you need to. The board has some comformal coating on it that you can scrape off the pads if you want with an exactoblade, although the soldering iron does a good job removing it.
    Thanks for the information. My batteries are constantly draining when the car sits for more than a week and I was told this may be another reason. I've checked alternator output and it's fine, so the GM is going to get some new parts. I've done circuit board soldering before, so this should be pretty straightforward....I hope.

  9. #34
    Join Date
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    E31/32/34 VWJetta A3TDI
    Hey folks... I just repaired another GM and created a PDF with photos.
    EEDegreeToDrive's Ultimate GM Repair Doc

    There isn't anything terribly new that Revtor, Spandrel and others haven't documented in the past, but I included my photos and tips, and added it to a PDF that can be downloaded/printed.

    Please take a look, and give me any feedback that you think it needs.
    I am planning to make it more complete and add the 2 GM removal processes, bad GM symptoms and failure explanations, and maybe some photos of GM repairs gone wrong (things not to do).

    Revtor: I borrowed your polarity image.
    Spandrel: Can I borrow your knee bolster removal instructions/photos and credit you?

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

  10. #35
    Join Date
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    Quote Originally Posted by EEDegreeToDrive View Post
    Please take a look, and give me any feedback that you think it needs.
    You wrote:
    and dropping the black plastic cartridge that holds the ZKE, GM, and RM
    Actually the RM is in the left door sill and the ZKE is not a module but a bunch of modules and relays controlled by the GM. The correct modules in that cartridge are from top to bottom the A3 lamp control module (LKM), A1 general module (GM) and A25 body electronics module (EKM).
    Revtor: I borrowed your polarity image.
    That's okay, but it's not world famous

  11. #36
    Join Date
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    Quote Originally Posted by revtor View Post
    You wrote:Actually the RM is in the left door sill and the ZKE is not a module but a bunch of modules and relays controlled by the GM. The correct modules in that cartridge are from top to bottom the A3 lamp control module (LKM), A1 general module (GM) and A25 body electronics module (EKM).That's okay, but it's not world famous
    Thanks, At one point I think knew which 3 modules were there. With an E34 and E32 in my fleet, it is easy to get them mixed up! Thanks again!

  12. #37
    Join Date
    Jan 2012
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    Upstate South Carolina
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    1996 840Ci / 2007 B7
    Quote Originally Posted by EEDegreeToDrive
    Hey folks... I just repaired another GM and created a PDF with photos.
    EEDegreeToDrive's Ultimate GM Repair Doc

    There isn't anything terribly new that Revtor, Spandrel and others haven't documented in the past, but I included my photos and tips, and added it to a PDF that can be downloaded/printed.

    Please take a look, and give me any feedback that you think it needs.
    I am planning to make it more complete and add the 2 GM removal processes, bad GM symptoms and failure explanations, and maybe some photos of GM repairs gone wrong (things not to do).

    Revtor: I borrowed your polarity image.
    Spandrel: Can I borrow your knee bolster removal instructions/photos and credit you?
    Absolutely- great job putting it all together in one place with tips and testing to boot!

  13. #38
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    Quote Originally Posted by Spandrel View Post
    Absolutely- great job putting it all together in one place with tips and testing to boot!
    I fixed the module descriptions Revtor; Thanks. BTW, your diagram is so famous I made a similar cheat card that I keep in the bag with my new capacitors (see attached)

    I think there should be 3-4 parts in a comprehensive GM repair manual:
    Part 1. Perform a current test to confirm- Detailed Instructions (and a picture or two) to determine if the GM is the cause
    Part 2a. Removing the GM via knee bolster (the easy way, w/ spandrel's photos)
    Part 2b. Removing the GM by dropping the module cassette (the fast way, but I need to document/capture next time)
    Part 3. Reworking the GM (which is already complete)
    Reinstall, retest (part 4) is mostly unnecessary.

    I am half tempted to lose my you-tube virginity and post a video of the re-cap procedure. I bet I could replace the capacitors in less than 10 minutes...
    Attached Images Attached Images

  14. #39
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    Folks--
    I just placed a order for more capacitors at Newark. If you don't want to risk damaging your GM and want me to do the work, send me a PM for more details.

    For reference, here are the Newark.com part numbers:

    Main Capacitor: 14M6702 (Vishay 470uF, 40V Low ESR, 10000 hrs @ 105C, 12.5x30mm) ~$2.77/ea

    For the Smaller Capacitors, I am going to try the brand Multicomp, they seem to have a smaller footprint than the Vishay ones I used before.
    97M3998 100uF 25V 105C 8x13mm ~$0.38
    97M3989 47uF 25V 105C 6x13mm ~$0.29
    97M4031 1uF 63V 105C 6x13mm ~$0.29
    97M4032 10uF 63V 105C 6x13mm ~$0.31

    Feel free to buy direct from Newark, but if you want, I can send out a kit of 5 caps for a reasonable price. I bought enough to supply a few other folks. I think I can ship out a kit for $8, + $4 for each extra set. If you want/need a set, send me a PM. I'm not trying to make a killing, just making sure the E31 GM population survives and no more modules are mutilated with wrong parts/shoddy repairs.

    Also-- I perform local GM repairs (DC Metro/MD area) for beer and good company...
    Last edited by EEDegreeToDrive; 01-24-2013 at 11:54 PM.

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

  15. #40
    Join Date
    Jan 2005
    Location
    Laurel, MD
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    I miss my E31!!!!!!!!!!
    Not sure about me being good company but I can bring beer if you want to check out the GM of my car. I don't have any issues or symptoms but does not hurt to have it inspected.

  16. #41
    Join Date
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    Quote Originally Posted by Ahmed303 View Post
    Not sure about me being good company but I can bring beer if you want to check out the GM of my car. I don't have any issues or symptoms but does not hurt to have it inspected.
    If we pull it out of the car and it has original caps, we might as well just change them. Pulling and replacing the module is 80% of the job!

    I'd be happy to get together again this winter or in the spring.. If the car/GM is not acting up, there is no rush.

  17. #42
    Join Date
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    E31/32/34 VWJetta A3TDI
    Quote Originally Posted by EEDegreeToDrive View Post
    Folks--
    I just placed a order for more capacitors at Newark. If you don't want to risk damaging your GM and want me to do the work, send me a PM for more details.

    For reference, here are the Newark.com part numbers:

    Main Capacitor: 14M6702 (Vishay 470uF, 40V Low ESR, 10000 hrs @ 105C, 12.5x30mm) ~$2.77/ea

    For the Smaller Capacitors, I am going to try the brand Multicomp, they seem to have a smaller footprint than the Vishay ones I used before.
    97M3998 100uF 25V 105C 8x13mm ~$0.38
    97M3989 47uF 25V 105C 6x13mm ~$0.29
    97M4031 1uF 63V 105C 6x13mm ~$0.29
    97M4032 10uF 63V 105C 6x13mm ~$0.31

    Feel free to buy direct from Newark, but if you want, I can send out a kit of 5 caps for a reasonable price. I bought enough to supply a few other folks. I think I can ship out a kit for $8, + $4 for each extra set. If you want/need a set, send me a PM. I'm not trying to make a killing, just making sure the E31 GM population survives and no more modules are mutilated with wrong parts/shoddy repairs.

    Also-- I perform local GM repairs (DC Metro/MD area) for beer and good company...
    Bump on capacitors still being available... Also, last time a forum member came up and we pulled his GM, I took a bunch of pictures. Shall I update the "Ultimate repair guide" with the From-the-bottom removal instructions as an alternative to Spandrel's remove-knee-bolster instructions?

    Edit: Alright.. I'll try to get to it by the weekend. ;-)
    Last edited by EEDegreeToDrive; 07-16-2013 at 12:13 AM.

  18. #43
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    1985 M635
    Yes please
    ================
    1985 M635 (gone but not forgotten)
    1994 850CSi (also gone but not forgotten)
    1985 M635 (current obsession)

  19. #44
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    spartanburg s c
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    1997 bmw840ci
    what is the part number for the general module ?
    thx!
    dl

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