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!
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?
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
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.Spandrel already gave you an excellent link (Success in General Module Repair) and there are plenty of other topics covering this repair...Also I have been looking for any pictures or tech info on how to remove the unit & where to start.
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.
Thanks for the reply,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.
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
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.
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?
'89 735i, '91 850i, '81 MB 380SLC (For Sale), Tesla Model 3, and VW Passat TDI -- Yes, I still repair General Modules, DM for info!
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).and dropping the black plastic cartridge that holds the ZKE, GM, and RMThat's okay, but it's not world famousRevtor: I borrowed your polarity image.
Absolutely- great job putting it all together in one place with tips and testing to boot!Originally Posted by EEDegreeToDrive
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...
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 10:54 PM.
'89 735i, '91 850i, '81 MB 380SLC (For Sale), Tesla Model 3, and VW Passat TDI -- Yes, I still repair General Modules, DM for info!
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.
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; 07-15-2013 at 11:13 PM.
Yes please
================
1985 M635 (gone but not forgotten)
1994 850CSi (also gone but not forgotten)
1985 M635 (current obsession)
what is the part number for the general module ?
thx!
dl
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