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Thread: E31 General Module Sleep Explanation, Experimentation, and Bench Testing

  1. #26
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    That is awesome news indeed!! Thank you for keeping at this.you did refurb my GM and I️ am still having the non-sleep issue. So, maybe another good test case?


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  2. #27
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    Nice- that's exactly what I went through to get mine working. I'm fairly certain the cause was the GM looking for the wiper pressure control. Good ideas on what causes the GM to get corrupted. I'd bet that the rest of the GM's that have been repaired and are still misbehaving are doing the same thing.

  3. #28
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    Quote Originally Posted by Timm View Post
    That's great news - we always had a suspicion that other modules (such as the EGS, seat and steering-column modules) 'reprogrammed' themselves to activate inputs and outputs for non-existent options and you have confirmed that with your tests. I don't think that is due to a failing module though - as this affects modules that don't actually fail (such as the EGS), it is possibly due to undetermined behavior under low-voltage conditions or something similar.....
    A primer for those you you new to this...
    EPROM = Electronically Programmable Read Only Memory (i.e. Write Once), some have UV windows to erase them - Maybe 16-256 Kilobytes
    EEPROM =Electronically Erasable, Programmable Read Only Memory (Overwrite) - 16-256 Kilobytes
    Serial EEPROM = Usually a small ~8 pin chip for saving manufacture data, configuration data (coding), faults; Much less capacity - 1-16 Kilo-bits

    Most of the ~dozen or so modules in our cars have 8-bit or 16-bit microcontrollers (Hitachi was popular in the 80s); likely with very similar circuit structures. (The door modules look just like the GM, but smaller, with 1/10th the I/O). It looks like the ~2-4MHZ Hitachi micros (GM/Door Module) have the program flashed in them and may be write-once EPROMS, so the firmware should be safe. (development ones were UV erasable). Of course, things like the GM can probably never be reprogrammed, and good luck replacing the chip and finding the firmware anyway! (Note, programming is not coding)

    Any module coding, or modules that can 'save' their faults (SRS), likely have a serial EEPROMs to supplement the EPROM. In the GM I think it was only a 1kbit Serial EEPROM, which is a surprisingly small 125 bytes!
    Note: That's probably ~12 bytes for manufacture info, ~10-20 bytes for coding, and the balance is probably for storing logged faults (each fault probably is logged with 10-12 bytes). Also note, Some of the options coding would only actually need a single bit! (feature enabled/disabled) It's important to realize that Serial EEPROMS or any kind of flash media have limited read-write cycles, sometimes it's tiny, like 1000 times. i.e. If you have a recurring fault in your car, it's possibly that over 20 years of recording faults you might exceed the limits of the serial EEPROM, and then all bets are off; but one could theoretically replace the part on the board if it failed. Some devices have sectors that have to be erased and rewritten in groups, so theoretically, one could segregate coding from faults, but this also means that to save one fault you might have to rewrite the whole sector of ~10 faults.

    Of course, the DME/EMLs are completely different.. Their firmware (and performance maps) are stored in external EEPROMS, but might have originally been EPROMS once upon a time. Other values, like engine faults, learned values, etc are saved in SRAM, which is why engine codes can be cleared by disconnecting the battery. (Not the case with modules like SRS, GM, LKM, etc)

    Back to your message, Timm..
    All of the modules with Serial EEPROMS need to have the hardware and firmware present to save coding/log things, so if any of the modules were subject to brownouts or other power fluctuations, static electricity, etc, then they too could jump program vectors or end up with corrupted stacks, etc. The primary difference is that the GM (and door modules) are powered all the time, where as many other modules are shut off most of their life. (The Hitachi CPUs were also known for their phenomenal sleep current specs, we had data loggers at a previous company with Hitachi 3003 CPUs that had nano-amp sleep currents, could run for 10 years on lithium primary batteries, customers didn't even realize they took batteries!)

    But yes, I suspect Door modules, GM, Memory seat modules, sunroof, LKM, EKM, SRS, steering wheel, and others could all end up corrupted under the right circumstances. However, a corrupted module may be less impactful than a GM that kills batteries..

    Possible effects of EEPROM corruption:
    Steering Wheel - LHD vs RHD bit flips--> controls reversed?
    Door module - LHD vs RDH bit flips? --> Maybe window controls stop working?
    SRS- How many ways can you code the SRS? Maybe a bit for a passenger side that doesn't exist -> trigger a fault?
    steering wheel memory -> Mine sometimes quits, doesn't want to move, etc.. My solution was to simply unplug one of the connectors.. still works in manual mode, but no memory function anymore
    seat/mirror memory -> fault? failure to save a position? failure to return to the correct position?
    LKM -> regional coding changes, indicates failure for bulbs that don't exist?

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  4. #29
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    Quote Originally Posted by adwebinc View Post
    That is awesome news indeed!! Thank you for keeping at this.you did refurb my GM and I️ am still having the non-sleep issue. So, maybe another good test case?
    Do you have anything setup to reprogram it? Using NCS Expert I was able to enter my Vin and coding keys off the sticker in my fuse panel, select just the GM and program..
    If you can't do this yourself, I'm happy to drop it in my car and reprogram it (so long as my car is still torn apart).

    Of course it's not feasible for me to drop customer modules in my car to do this every-time, nor should everyones' modules be coded to my generic USA spec car (or be expected to work if my car doesn't have the same options as a customers')
    Ideally, at some point I'll be able to bench test and bench program them, and have folks send a photo of their coding key just in case.

    Quote Originally Posted by David9999999 View Post
    Nice- that's exactly what I went through to get mine working. I'm fairly certain the cause was the GM looking for the wiper pressure control. Good ideas on what causes the GM to get corrupted. I'd bet that the rest of the GM's that have been repaired and are still misbehaving are doing the same thing.
    Yeah-- I was hoping so, but so far, out of a sample set of 2, I'm only at 50%.
    John C sent me a module to fix earlier in the year, I did it, shipped it back to him, and it still didn't work properly.. He sent it back to me and I confirmed it didn't work in my car. Of course, I learned later that his car was from France that was 'brought to US specs" so who knows what it has or doesn't have. I suspect he would still have options in his car that most US cars don't. In either case, i ended up sending him one of my spare modules and getting him up and running. (though his US spec-coded module won't be able to operate any non-US features like headlight washing or wiper pressure control without appropriate recoding-- email out to him).

    I did try flashing John's module (now my module) to US spec and repeated the current test.. It didn't solve the problem, so I need to figure out if there is something else going on with his module, or if I'm still missing something.

    If I'm able to bench check these modules and read the coding and faults on my bench then I'll be able to determine if it's corrupted (or just coded differently), but re-coding a corrupted module (10% of them?) might add a significant cramp in my style. Bogus manufacture dates and "Unknown" faults are a dead giveaway, and something I don't know if I can actually change, short of replacing serial EEPROMS with a pre-programmed one. But the other interesting thing about a bench setup is that I'll need to include the proper inputs to satisfy alt-coded GMs (i.e. my test bench will need to fake the I/O for headlight washers, wiper pressure control, etc if I expect a ECE coded module to sleep on my bench)

    I still don't know 100% what happens in the absence of door modules, sunroof modules, EKM, etc. but I also don't want my bench test log a bunch of new faults that I can't erase easily.
    Last edited by EEDegreeToDrive; 11-09-2017 at 02:16 PM.

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  5. #30
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    Interesting that the US module was able to work in the Euro car without a sleep issue. When you put the re-coded module into your car and it didn't work, what faults (if any) were logged?

  6. #31
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    You are an engineering beast my friend . The GM you soldered for my CSi is still trouble-free thankfully...but it's awesome reading all this info.
    Last edited by shogun; 04-09-2020 at 10:09 AM.
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  7. #32
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    Quote Originally Posted by David9999999 View Post
    Just did some quick googling and figured out that ADV is the "Anpressdruckverstell," or "adjusting contact pressure" in English. So, my theory is the GM was replaced by the PO with a unit from a European car. In my car, it was looking for the wiper pressure adjustment and could not find it.
    I think it's more than likely that the module is corrupted and/or reverts to European coding when things go awry, since the ~2 of the modules I've messed with this week seemed to do the same thing.
    Kevin's module was manufactured the 52nd week of 2047; Zach's was manufactured the 54th week of 2044

    Quote Originally Posted by adwebinc View Post
    That is awesome news indeed!! Thank you for keeping at this.you did refurb my GM and I️ am still having the non-sleep issue. So, maybe another good test case?
    Zach-- (You already know this because I texted you)
    Your GM had corrupted itself (or defaulted to?) to ECE/Europe(bad), with coding for Sunroof (correct), Door lock heating(correct), HL/CL system (headlight washers, bad), intensive cleaning (standard issue in US), and WWPC (Wiper pressure control aka ADV). Without the APV relay in your car I suspect that's why it wasn't going to sleep.

    Unfortunately, your module, after it was recoded to US spec, still did not sleep afterwards. Hmmmmph. (I also opened it back up and reinspected/double checked my work, nothing out of the ordinary revealed)
    EDIT!! I put the module back in the car, took it out for a spin, checked the coding again (looked OK). I did see another stored fault for APV, so I tried recoding it again just for fun... Anyway-- pulled it back in my garage, repeated the current test, and viola, sleeping, 40mA. It healed!

    Another module that a member sent back to me, not working properly after repair, also appeared to be corrupted (ECE coding, WWPC, etc), that is until I found out it was originally from a Grey Market/France car with European options and No Sunroof, imported into the US. (So yeah, it wouldn't have tested properly in my car, as-is). Since he was still having an issue with it, I had sent him a US spec module last year (not realizing he actually had a ECE car) and it seemed to worked fine in his car. (Though I suspect his headlight washers and wiper pressure control probably don't work). Regardless, because his original module still had a current problem, I dropped it in my car, recoded it for US, and repeated the current test. Unfortunately, it still had a lack-of-sleep problem.

    Quote Originally Posted by David9999999 View Post
    Bumping this thread- I recently fixed my GM "awake" issue on my car. With the help of a friend of mine and some files from revtor, I was able to get INPA/NCSExpert set up on a dedicated computer to read the errors on the modules in my car. I found that the GM had an error for the windshield wiper pressure control (my car is US version and does not have this option), as well as an error for the "DRM 2 ADV" (not sure exactly what that is, but I also found references for it on euro cars only).

    I used NCSExpert to reset the module to factory, and my car now enters sleep mode correctly, with a resting current between 50-60 mA. My car did not exhibit any electrical issues before or after the coding process. Really happy to have solved this on my car!
    Yes--
    My procedure has been the following:
    1) Confirm bogus coding with INPA (can't hurt anything to play in INPA)
    2) Close INPA and launch NCS expert; Load Expert profile.
    3) Hit F1 and Enter VIN number and other coding lines (found on the fuse panel sticker, most US cars should have the same coding, include the extra digit at the end of each line as a checksum, and if you DON'T select 'calculate checksum', it will veerify that last digit as a checksum to make sure you typed it correct)
    5) Click Back to exit VIN entry, then pick Process ECU
    6) Select Module : GM2 (You want to be careful NOT to reprogram everything in the car, just the GM)
    7) Verify Default Action is to code module (but you should only see GMII listed)
    8) Execute Job, and shut everything down.

    Disconnect battery and reconnect a few seconds later. (The GM needs to restart I believe)
    Turn ignition key on, Fire up INPA and double check coding... Should look reasonable now.
    Clear all the GM errors as a good measure (there's probably a bunch of bogus codes, including things like missing Wiper Pressure Control (aka APV)
    Repeat current test..


    Mini-Summary--
    Of the ~50-75 General Modules I've repaired, there have been 3 (or maybe 4) cases where the car still wouldn't sleep after the capacitor replacement.
    3 of these were corrupted (or defaulted) to ECE spec coding, with options not typically found in USA spec cars.
    2 of my 3 were fully functional after recoding (sometimes twice) to US spec options.

    Granted, NCSExpert reprogramming only changes the options, and these modules also exhibited bogus looking coding of manufacture date. Perhaps with a little more work, some help from NCSDummy, and learning a little German, maybe one of my scripts can be modified to 'fix' other corrupted fields.. I suspect there will come a time where I may need to replace a Serial EEPROM and reprogram it, plus it would be neat to update the manufacture date with the GM capacitor refresh date (particularly if it's corrupted to 2044/2047 anyway)
    Last edited by EEDegreeToDrive; 11-18-2017 at 06:47 PM. Reason: "Bad" module healed!

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  8. #33
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    Nice that you got another fixed with the coding! I wonder if the last one that is still not fixed would also be throwing codes for APV, or something else. I think that driving around and using the car is an important step to see what codes, if any, pop up from the GM. When I was first playing with INPA and not recoding, I had several APV errors come up within one day from driving the car around. After re-coding, they did not come back.

  9. #34
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    Tremendous gratitude to Scott for his work in my module!! I will report back once I received the “healed” module on the results once back in the car.

    Thank you Scott!!


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  10. #35
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    Hey David I am in Brooklyn. For a few months now low washer fluid come on my OBC. Parked car Friday, snowed Saturday, Tuesday went to start. Nothing DEAD. Batteries completely drained. Wont even take a charge. I was told by my good buddy ED 8 series enthusiast in Cali. It's my GM. Even though I have owned a 850 since 1999 I have not encountered this before. But there's a 1st time for everything. I was hoping you might assist me with recoding my GM since were both in the NYC area. If possible I'm hoping you can give a fellow 8series guy a hand in solving the matter. I'm going to get new batteries today but I want to address this issue before I hook these bad boys up. I don't want to kill these too. Any help given by any and everyone will be greatly appreciated. Thanks guys. Let keep these machines on the road. Nay 917-652-9184

  11. #36
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    3 days is quick for a battery drain. Have you measured the drain with a multimeter? Any other symptoms? That would give us some idea of what's going on.

    I'll send you a PM about reading codes.

  12. #37
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    Quote Originally Posted by Dirtboy Nay View Post
    Hey David I am in Brooklyn. For a few months now low washer fluid come on my OBC. Parked car Friday, snowed Saturday, Tuesday went to start. Nothing DEAD. Batteries completely drained. Wont even take a charge. I was told by my good buddy ED 8 series enthusiast in Cali. It's my GM. Even though I have owned a 850 since 1999 I have not encountered this before. But there's a 1st time for everything. I was hoping you might assist me with recoding my GM since were both in the NYC area. If possible I'm hoping you can give a fellow 8series guy a hand in solving the matter. I'm going to get new batteries today but I want to address this issue before I hook these bad boys up. I don't want to kill these too. Any help given by any and everyone will be greatly appreciated. Thanks guys. Let keep these machines on the road. Nay 917-652-9184
    The GM capacitors at end-of-life are usually the first problem that leads to a power drain.
    Edit:Your module shouldn't need recoding unless you're in the ~<5% where capacitors alone don't fix your problem.

    Under normal operating conditions, 2x 85AH batteries with a 50mA draw (0.05A) will last 3400 hours, 141 days, or 4-5 months, and that's provided the batteries are brand new, fully charged, and behaved like deep cycle batteries (they don't). Further, it would take a 100A alternator with the engine running over 1500RPM close to 2 hours to fully charge dead batteries, and that's given no other loads and 100% efficient charging. All that said, A properly functioning car shouldn't need a trickle charger provided it gets run for an hour or two every 3-4 months.

    Now-- For a car with a bad GM, typical load may be 0.5A-0.75A, 10-15x normal. The short math is that the car can only sit 1/15th as long with a bad general module. Two 85AHr batteries with a 0.5A high current draw will only last 340hours, or 14 days. Now, if your car is having problems with the general module, and you only drive it ~30 minutes a week, your batteries will never really get charged. Also, if your batteries get real low (and/or cold outside), then the bad GM may start rebooting and cycling the relays, so current may cycle between 0.5A and 1-2A, which can kill the batteries in ~3-4 days. It's these cycling events that I believe could lead to the GM's programming getting corrupted/scrambled.

    Edit: When batteries are dead, the plates sulphate.. The more time (days) batteries spend dead, the more sulphation occurs. Some sulphation is reversible with a pulse-based trickle charger. Some folks will swear by their expensive CTEC chargers, but I've revived many "dead" batteries with my $20 craftsman charger. I strongly advise folks pick up a load tester https://www.amazon.com/Schumacher-BT.../dp/B000AMBOI0 and learn how to properly use it (wait till batteries are fully charged before testing) before they throw $300-500 in batteries at the car every 3 years. In BMWs like the 7 and 8 series, where batteries are protected from the elements, batteries can easily last 5-10 years.
    Last edited by EEDegreeToDrive; 12-14-2017 at 08:08 PM.

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  13. #38
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    A huge thank you for all this extremely valuable information. I currently have a Dutch 850i in my shop where I replaced all GM capacitors but the car still refuses to fall asleep.
    Since on most ECE cars (as a matter of fact on ALL I've been doing a read out on) the ADV is not working I now wonder on how many the GM's programming is corrupted.
    Thanks again for the phantastic work.

    Last edited by wokke; 12-17-2017 at 08:15 AM.



  14. #39
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    Quote Originally Posted by wokke View Post
    A huge thank you for all this extremely valuable information. I currently have a Dutch 850i in my shop where I replaced all GM capacitors but the car still refuses to fall asleep. Since on most ECE cars (as a matter of fact on ALL I've been doing a read out on) the ADV is not working I now wonder on how many the GM's programming is corrupted. Thanks again for the phantastic work.
    No problem! To clarify: The corrupted programming seems to be a result of a misbehaving general module, but the inconsistent-state software bug is the reason the car doesn't go to sleep afterwards.
    As I discovered earlier in a USA car, pulling the Wiper relays will cause the GM to fail to sleep because it can't confirm the inconsistent state received. Some other conditions, like the doors, seem to resolve themselves on the second sleep cycle (32 minutes!)
    Of course, all of this is subject to very if there are different versions of the GM ROM (can anyone confirm?) There are certainly different hardware versions.
    My suspicion is that a car coded for APV will not sleep if
    a) the car doesn't actually have APV,
    b) If a car DOES have APV, but the relay is removed
    c) If a car DOES have APV and there's some other problem with the APV system.

    Things I don't know and need further testing if there's any volunteers--
    What happens when a car has modules that it is not coded for--
    1) What if your car DOES have APV, but it's not coded for it? Does it still sleep? Does APV work?
    2) What if your car DOES have Sunroof, but it's not coded for it? Does it still work? Can it still be opened/closed from the key?
    3) What effect does having (or not having) headlight washers and being coded (or not coded) for? (They don't have the same feedback as the wipers, so might not be as vulnerable to bad coding)

    Too add confusion: I've seen other cars programmed with otherwise fine acting GMs show strange manufacture week/years. A module I checked out the other day had normal looking coding, but was still manufactured in week 44; perhaps a bug in an INPA script? Can anyone else with a working INPA system add your manufacturing info from your GM?
    Last edited by EEDegreeToDrive; 12-18-2017 at 05:58 PM.

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  15. #40
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    Scott - an interesting update with my repaired / recoded GM... so the consumer relays are no longer firing after the car is off (they used to do so well after the sleep cut off). Also, I don’t notice the odometer light randomly coming on any more. However, the trunk lights do NOT go off after 17 minutes. Anything else I should check?


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  16. #41
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    Did you actually do a current test after the module was reinstalled?

    The trunk lights DO go through Consumer Cut-Off Relay #1, as do the glove box lights, and the power for consumer cut-off relay #2 (all fed from CCOR#1)
    Do the trunk lights shut off as soon as you pull the consumer relays? (They should - if not, maybe you've got a short in your trunklid). Turn on one of your map lights too-- they should all go off after 16 minutes.

    If your having problems with your doors, try waiting 32 minutes for a second cycle. Remember you can't open the doors during the test

    CCOR#1 has pin 30 +12V, and then 87/87A are bridged together and switched. Any chance your relays got mixed up and a different relay is present? (with different pinouts?)

    Do the current test and report back.

    Quote Originally Posted by adwebinc View Post
    Scott - an interesting update with my repaired / recoded GM... so the consumer relays are no longer firing after the car is off (they used to do so well after the sleep cut off). Also, I don’t notice the odometer light randomly coming on any more. However, the trunk lights do NOT go off after 17 minutes. Anything else I should check?


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  17. #42
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    As a minor but probably very important detail, what brand of capacitors do you use for replacement on the general module? Original ones on mine were Panasonic and I believe there are some very crappy brands out there which would be as bad (especially in cold) as dead compared to a good brand.

    Thanks,

    Ozzie

  18. #43
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    While we're on the subject - I decided to write up the easy method for measuring battery drain - and even did a video this time!

    http://www.meeknet.co.uk/e31/E31_Bat...iagnostics.htm
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  19. #44
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    Quote Originally Posted by turquise1 View Post
    As a minor but probably very important detail, what brand of capacitors do you use for replacement on the general module? Original ones on mine were Panasonic and I believe there are some very crappy brands out there which would be as bad (especially in cold) as dead compared to a good brand.
    Are you sure it had Panasonic? I've seen a lot of general modules (GM) from the very early years up to modules that were manufactured long after E31 production had ceased, and they all used Philips (blue) and Roederstein (yellow) electrolytic capacitors:

    • 1µF / 63V / -40..+85°C / Philips 021K0 series
    • 10µF / 63V / -40..+85°C / Philips 021K0 series
    • 47µF / 25V / -40..+85°C / Philips 021K0 series
    • 100µF / 25V / -40..+85°C / Philips 021K0 series
    • 470µF / 40V / -40..+85°C / Philips 021K0 series or Roederstein EBM series

    These are pretty much "standard" capacitors. They are not designed for extra long life or extreme temperature conditions but they are certainly not poor quality. After all they did last 15+ years in hot and cold climates. They may be under-specced for the application, though. Someone cheaped out here... For example, the body electronics module (EKM) and the light control module (LKM) use much higher quality Nippon Chemi-Con KMF and SXE series electrolytic capacitors with an extended -40..+105°C temperature range.

    By the way, both Philips and Roederstein sold their capacitor divisions to Vishay and the exact same capacitors as used in the E31 GM can still be bought today, albeit Vishay branded (datasheets Vishay 021 ASM and Vishay EBM). Axial leaded capacitors are quite hard to come by nowadays so these capacitors may still be a viable option for the GM if you want to achieve OEM appearance. They'll last at least another 15 years.

    If you don't mind using radial leaded capacitors you have a much broader selection to choose from. The original capacitors have about average specs but you may want to choose capacitors with low(er) ESR, wide(r) temperature range (-40..+105°C) and better ripple current characteristics.

    If you are looking for top brands, go with Nichicon, Nippon Chemi-Con (rebranded as United Chemi-Con and Europe Chemi-Con in some parts of the world), Panasonic or Rubycon. There are more but every serious distributor should carry at least one of those.
    Last edited by revtor; 01-11-2018 at 12:32 PM.

  20. #45
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    Sorry, if I caused any confusion but I am replacing the ones on GM3 (E53) which has all Panasonic capacitors. I first replaced them with some brand called NTE and then read they were not very reliable particularly in cold, so I ordered Panasonic brand from Mouser. Thanks, Ozzie
    Last edited by shogun; 04-09-2020 at 10:12 AM.

  21. #46
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    Revtor--
    Yes, The original capacitors are Philips ones, but rated at 105C I believe, which makes them a little special. I think the EML had a few 125C parts. For the GM, I've used 85C and 105C capacitors over the years, but decent brands. Interestingly, the Vishay axial ones @ 125C are huge and certainly don't fit; I ended up with a batch of 85C Vishay caps one point that fit very well, but my latest parts list typically includes 105C caps from Multicomp that need a little coercing to fit (at least the 100uF) but i feel more confident about.

    For anyone interested.. Temperature ratings on capacitors are like speed ratings on tires.. Does the general module ever get up to 125C, or even 105C (boiling)?? Of course not.. Granted, A capacitor rated 5000Hr@105C will last longer than one rated 5000Hr@85C, especially since neither runs at those temperatures. (In comparison to tires... A tire with a speed rating of 168MPH will likely still outperform a 130 MPH rated tire, even if you're only driving 80 most of the time) In the General module, those caps have been running 15-25 years, non-stop, since the general module always has power, even with the car off, which is >200,000 hours; Pretty decent for a part designed and installed 25 years ago IMHO!)

    All that said, the Roederstein one (the big one) is likely the one that fails, and I'd bet most general modules would behave just fine if only that one 470uF/40V cap was changed. (Also of note, In the EML that I repaired, it was a Roederstein cap that had shorted.) Regardless, I change them all (Though, there were a variety of specialty caps in the EML, including a Tantalum and a few low ESR caps).
    In the General Module, for the main capacitor, I have always used a Vishay 470uF/40V cap that's rated to 105C, and fits perfect. (It's also the most expensive part of the repair, aside from shipping, at like $5 part in small quantities, IIRC)

    I'm getting ready to do another parts buy in a few weeks and will update this thread with the latest and greatest in my list. I've got a few scratched down on paper that work (and don't work).

    Finally-- I'm not a fan of folks using Radial parts instead of the proper Axial leaded parts.. They're usually procured at local electronics shops, cheap parts, and look terrible when installed. I've certainly seen hack jobs where leads have broken off. (Combination of poor solder techniques, cold solder joints, and folks just tacking them on to existing leads they didn't bother to remove/clean properly.) IMHO, If you can't procure the proper parts for the job, you probably shouldn't be doing it.. Otherwise the modules end up in my hands for fixing a second time.. "Yeah, the previous owner said it had a power drain and they tried to fix it... ". I also reapply a layer of conformal coating to the capacitors, which does serve to glue them in a little bit in addition to the primary benefit of keeping condensing moisture off the metal.
    Last edited by shogun; 04-09-2020 at 10:13 AM.

    '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!

  22. #47
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    Quote Originally Posted by EEDegreeToDrive View Post
    The original capacitors are Philips ones, but rated at 105C I believe, which makes them a little special. I think the EML had a few 125C parts. For the GM, I've used 85C and 105C capacitors over the years, but decent brands. Interestingly, the Vishay axial ones @ 125C are huge and certainly don't fit
    The original capacitors in the GM really are 85°C. But that's okay. Even the AEC-Q200 automotive standard demands only -40..85°C for applications in the passenger compartment. Given the rather average specs of the original capacitors pretty much any replacement will work fine. As long as you stick to quality brands there's little to worry about. It does not hurt to go with better specifications, of course. If available I'd definitely go with -40..105°C capacitors.

    125°C would be a waste of money, though. These capacitors are meant for under-hood applications where engine heat causes very high operating temperatures (like for example the EML you mentioned). That's not applicable to the GM.

    Finally-- I'm not a fan of folks using Radial parts instead of the proper Axial leaded parts.. They're usually procured at local electronics shops, cheap parts, and look terrible when installed.
    The major advantage of radial electrolytic capacitors is availability. It is much easier to find decent quality radial electrolytic capacitors at low cost than axial ones. Axial capacitors are on the way out. Many manufacturers and stores don't even carry axial electrolytic capacitors anymore or have a very limited product range. Naturally axial capacitors are preferred for this job but when done properly it's perfectly fine to use radial capacitors. Sure, it will not look as pleasing but it works just as good.

    I do fully agree with you that securing the components (with conformal coating or silastics) is important to reduce the stress on the solder joints - even more so when using radial capacitors.

    However, leads breaking off, solder joints failing, low quality parts,... have more to do with the person that repaired the module than the choice of capacitor lead style. If you can't make radial capacitors to work reliably, there's little reason to assume that the result would have been better with axial capacitors...

  23. #48
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    My apologies! I just checked 2 original modules and my trash can that contained examples of the Rod and Philips parts, and sure enough all were 85C so I stand humbly corrected! It's been so long since I've selected the parts in my bins and since I've always used the Vishay 138 AML for the 470uF/40V cap which is 105C (Newark #14M6702), I suppose I've been thinking that 105C was best for the whole job. That makes me feel better about the many dozen general modules I've fixed that have 'only 85C' parts for the smaller capacitors. Of course, at some point I bought 50-100/ea of the 85C Multicomp parts which fit quite well, so I suppose I did know that 85C was acceptable all along.
    Last edited by shogun; 04-09-2020 at 10:14 AM.

    '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!

  24. #49
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    After all the GM repairs and correcting many problems in the car, I am still having issues with car going to sleep. Couple of interesting things..

    The car actually goes to sleep when I have a multimeter attached serial to check the current (Amp) drain.Tried to figure out how a multimeter would affect the system (I have used two different multimeters, they both 'helped' the sleep) but not sure. Also temperature still affects the sleep. When its around 30f+ outside, the sleep actually happens. Would the IHKA module somehow interrupting the sleep? Would capacitor change on IHKA as well somehow help?

    I have checked K72 (consumer cutoff) relay as well and it seems ok.

    Any other ideas?

    Thanks,

    Ozzie

  25. #50
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    Have another go at measuring the battery sleep current using this method:

    http://www.meeknet.co.uk/e31/E31_Bat...iagnostics.htm

    The result where your car went into sleep mode with one of the meters shows that the closed-circuit current (sleep mode) is working correctly, and the method of measuring was the original problem!

    https://youtu.be/2CCMZxD8Hwo
    Last edited by Timm; 01-20-2018 at 10:19 AM.
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