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Thread: EML Capacitor Replacement

  1. #1
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    EML Capacitor Replacement

    Hi Folks--
    Ed sent me his GM for repair a few weeks ago and I said I'd look at his EML I finally got around to it..

    He reported the throttle plates were acting funny and one bank wasn't running. There was no obvious damage, but one of the aluminum electrolytic caps didn't look great. We decided to proceed and replace the capacitors.

    There were a few general purpose caps in there, but there were also a few 'special' ones, including a Tantalum capacitor, a Philips aluminum can, a Fraco 100uF 10V, and some Roederstein EK sealed/baked capacitors commonly used in the Audio industry.
    (There is also about 50 ceramic capacitors and about 100 early surface mount resistors in there too!). I replaced 8 capacitors altogether, cleaned and coated the board, and dropped it in my 1991 850i. It started right up and I took it out for a spin. Everything seems to work fine, cruise, idle, etc. I didn't do any kind of programming or throttle calibration, just took it for a spin.

    Upon return, I measured the resistance of the old capacitors, (the meter in front of me doesn't measure capacitance) and most floated up to 6M-ohm, except the Fraco, which measured a short circuit, 0.1ohm, perhaps it was the problem?

    I replaced most with Panasonic FC series, which were 105C operating temp and low impedance. Interestingly, capacitors have changed enough in 25 years that many were actually smaller that the originals, though no heroic measures needed to be made.

    Capacitors Used:
    2x Generic 220uF 63V 105C (Replaced with Panasonic FC Series, Newark #49W7101, $0.585/ea)
    2x Generic 100uF 25V 105C (Replaced with Panasonic FC Series, Newark #96K9155 $0.147/ea)

    ROE 220uF 40V (Popular on Audio forums, Replaced with Panasonic FC Series,220uF 50V, Newark #49W7044 $1.03/ea)
    Fraco 1000uF 10V (Replaced with Panasonic FC Series, Newark #25M9148 $0.73/ea)
    (EDIT/NOTE: In my diagram lower-right, I labeled the Fraco one 100uF when it's actually a 1000uF; Thanks for noticing Albert850i!)

    Philips 220uF 10V Low ESR 105C (Replaced with Panasonic 220uF 16V, OS-CON Series, Low ESR, 0.013ohm, Newark #98W0174 $1.23/ea)
    Unknown 200uF 10V Tantalum (Replaced with Vishay 100uF 10V, 150D Series, Axial, Newark #65F2330 $4.57/ea, I also had ordered a KEMET Tantalum #70K8848 @$4.00/ea)

    Disclosure: I don't know what's so special about the ROE or Fraco capacitors, but I used pretty decent Panasonic caps that I hope are suitable quality. I also used them in place of the generic caps which is probably overkill.
    Also, The Tantalum cap I used is rated 2000hrs@85C and derated to 1000Hrs@125C. The higher temp mil-spec ones were $5-6/ea, out of stock, and had 20pc minimum. Regardless, Assuming 60MPH, that's 120K miles if the capacitor is operating near boiling temperatures. In short, some of these capacitors might not last another 25 years, but should last at least 10!

    ALSO NOTE: This was a 0 205 000 004 EML presumably from an Early model 850i. I swapped out my 0 205 000 015 EML with it and it worked fine, but other EMLs may have different parts!

    If folks start sending me their EML's for capacitor replacement, I'll order the MIL-spec ones. Anyone have any dead EMLs lying around they might want to donate to me for experimentation/spares ? Or pay to have experimental surgery?

    eml.jpg
    Last edited by EEDegreeToDrive; 08-03-2018 at 09:48 PM. Reason: Added capacitor info, disclosure

    '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!

  2. #2
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    Scott, thank you so much for taking this on, I know this was outside of your usual realm but it was a success!
    The EML you fixed for me was 0 205 000 004,it was from a pre 1991 6 speed car. It will be a very good spare to have on my shelf.
    Thanks again! Will be sending you another GM.

  3. #3
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    Quote Originally Posted by dragon850 View Post
    Scott, thank you so much for taking this on, I know this was outside of your usual realm but it was a success!
    The EML you fixed for me was 0 205 000 004,it was from a pre 1991 6 speed car. It will be a very good spare to have on my shelf.
    Thanks again! Will be sending you another GM.
    Thanks-- (I updated my post to reflect -004, not -005)
    In any case, it seemed to run just fine in my 1991 850i/Auto.

    I wonder though if the -004 EML (for a manual) is less prone to the double-limp-home syndrome. In the Autos, if you lose a bank and are running on 6cyl (aka Catalyst Protection Mode, not actually called Limp Home), the car still has enough power to get around. However, if you step on the pedal too far, which is easy to do when running on half-an-engine, the transmission module (EGS) gets upset with the lack of acceleration and goes into Transmission Failsafe mode (also not called Limp home mode), which then commands the engine to limit the RPM, effectively kicking the car further down the stairs while its already fallen down. Catalyst Protection combined with Transmission Failsafe basically limits the one working bank to only ~2500RPM, and generally locks the user into 3rd gear, which is more like "crawl home" instead of "limp home". It seems to me this combination of 'protection' wasn't really thought through very well. Glancing at the ETM for the EGS, there is an 'Injection signal' from the EGS to DME (presumably for cutting off the injectors between up shifts), also pin 24 (BRN/GRN) goes to both DME's, and pin 4 (GE/GRN) goes from EGS to EML; one of these is probably the signal that causes the engine to respond to transmission failsafe, right? Do the EMLs get programmed for manual mode? If so, does a manual-programmed EML still have a transmission failsafe input that's monitored?
    Last edited by EEDegreeToDrive; 06-11-2017 at 09:17 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!

  4. #4
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    Thanks for posting.

    So is it confirmed that replacing these capacitors fixed the original complaint of the throttle bodies acting up?

  5. #5
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    In my sample size of 1, it appears so. If you want me to expand my sample size to 2, shoot me a 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!

  6. #6
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    I have 3 "sick" 015 EMLs if you want to play with them sir!
    91 850 (Panzer), 2012 Mini Cooper Countryman (WifeMobile) www.wuffer.ca


  7. #7
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    Scott, I have a dead EML I'd love to send you.

    Sent from my Nexus 5 using Tapatalk
    I swear, my cars are like a girlfriend.
    Sometimes its a rough ride, sometimes its smooth motorin'.
    Sometimes she doesnt like how i treat her and sometimes i dont like how she behaves.
    BUT at the end of the day, she loves it when I am inside her.

  8. #8
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    Quote Originally Posted by clockwork View Post
    Scott, I have a dead EML I'd love to send you.
    PM Sent
    Quote Originally Posted by Wuffer View Post
    I have 3 "sick" 015 EMLs if you want to play with them sir!
    But I'm still backlogged a pair of your climate control swords to operate on! Are you sure you want to send me more stuff! :-)
    I did look at them again the other day... I need to drill out the rivets, remove the heatsink, chisel off the epoxy, cut out the parts and save the spacers, solder and coat the new parts, if I can find the bag/tube of FETs, and then re-secure things!



    Seriously though folks-- It's 2-4x the effort of the GM repair due to the assembly, costs a bit more to ship, and the 'fix' may not be nearly as successful as the GM trend.. Is it worth a $100 gamble? How much are these modules worth and/or going for on eBay?

    Also, Right now I'm doing 11hr days at my Engineering day job (thanks to the ~1+ hr commutes), plus I'm understudying a role at a local theater company that's a bit over my head and may consume me for the next month! That said, It's way too hot in this house, I'm headed down to my mad scientist lab to rip apart Tom's swords..

    '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!

  9. #9
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    @EEDegreeToDrive: I am also planning to replace the main EML capacitors, however, did not manage to split the two boards. Can you explain how the upper board can be slid out of the black connector?

  10. #10
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    Quote Originally Posted by Albert850i View Post
    @EEDegreeToDrive: I am also planning to replace the main EML capacitors, however, did not manage to split the two boards. Can you explain how the upper board can be slid out of the black connector?
    If I recall, There's a few white plastic pieces that pull out, then there is a tab on the black connector.. It takes a bit of force but it eventually comes free.. Separating the board was the worst part of the job!

    If you want/need, I can probably assemble a parts kit and maybe save you a few bucks--- I got a slight bulk discount on a few of those parts, (ordering qty 10 and such)

    '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!

  11. #11
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    Quote Originally Posted by clockwork View Post
    Scott, I have a dead EML I'd love to send you.
    @clockwork, Did we ever do your EML, was it a success? What was it doing before?

    Quote Originally Posted by Albert850i View Post
    @EEDegreeToDrive: I am also planning to replace the main EML capacitors, however, did not manage to split the two boards. Can you explain how the upper board can be slid out of the black connector?
    @Albert850i did you ever get your EML operated on? What was it doing before?

    Aside from @dragon850 's EML which was dead or intermittent, I'm wondering what other, if any, ailments EML reconditioning solves.

    '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!

  12. #12
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    Have not started again with my EML. My plan is to replace all capacitors in all ECU's, to increase reliability (as apparently capacitors were never designed to live over 20 years..). Will keep you posted.

  13. #13
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    EEE, I did not send you the dead EML yet. I'd still LOVE to tho.
    It just stopped working one day, no idea why. No burnt smells or any evidence of what could have gone wrong.
    I'd like to see if you can attempt to fix it whenever you have time (no rush)...
    I was going to send it to you the same time I send you my GM for preventative maintenance. No problem with my GM after 28 years, but still should send it to you I fear.
    I swear, my cars are like a girlfriend.
    Sometimes its a rough ride, sometimes its smooth motorin'.
    Sometimes she doesnt like how i treat her and sometimes i dont like how she behaves.
    BUT at the end of the day, she loves it when I am inside her.

  14. #14
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    Quote Originally Posted by EEDegreeToDrive View Post
    If I recall, There's a few white plastic pieces that pull out, then there is a tab on the black connector.. It takes a bit of force but it eventually comes free.. Separating the board was the worst part of the job!
    Managed to open it, by releasing the locks at both ends and opening the two wide black tabs which keep the sub-connector in position.
    I have soldered in 8 new caps, but do not have a tool to check the old ones. Ohm meter shows climbing resistance, probably as the caps are being charged; possibly they were all still OK.
    Note that your sketch shows a 100 uF - 10V cap on the right hand board, which should be 1000 uF - 10 V.

  15. #15
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    If folks start sending me their EML's for capacitor replacement, I'll order the MIL-spec ones. Anyone have any dead EMLs lying around they might want to donate to me for experimentation/spares ? Or pay to have experimental surgery?

    Hey, I have a cb00168 (03/90) build which I will be sending you my GM for preventative maintenance work over this fall so I can send you my dead (not sure why) EML too for you to play with.
    Mike



    Sent from my Nexus 5 using Tapatalk
    I swear, my cars are like a girlfriend.
    Sometimes its a rough ride, sometimes its smooth motorin'.
    Sometimes she doesnt like how i treat her and sometimes i dont like how she behaves.
    BUT at the end of the day, she loves it when I am inside her.

  16. #16
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    Quote Originally Posted by clockwork View Post
    EEE, I did not send you the dead EML yet. I'd still LOVE to tho.
    It just stopped working one day, no idea why. No burnt smells or any evidence of what could have gone wrong.
    I'd like to see if you can attempt to fix it whenever you have time (no rush)...
    I was going to send it to you the same time I send you my GM for preventative maintenance. No problem with my GM after 28 years, but still should send it to you I fear.
    Sounds good-- Ship them together. I'll of course get the GM turned around ASAP as I always do; but will message you about how you want to handle the EML.

    Quote Originally Posted by Albert850i View Post
    Managed to open it, by releasing the locks at both ends and opening the two wide black tabs which keep the sub-connector in position.
    I have soldered in 8 new caps, but do not have a tool to check the old ones. Ohm meter shows climbing resistance, probably as the caps are being charged; possibly they were all still OK.
    Note that your sketch shows a 100 uF - 10V cap on the right hand board, which should be 1000 uF - 10 V.
    Thanks for noticing that.
    Ohm meter climbing is correct for a capacitor.. the time it takes to go open-circuit is proportional to the capacitance, but without a capacitance meter, tough to get an exact figure. If they don't end up open-circuit (or at least in the meg-ohm range), it might indicate a problem. In my case, one of the capacitors was simply shorted after removal. There's tons of other things that could have failed in the EML. look for discoloration or any evidence of excessive heat. Might have a bad transistor or two. If it had a specific problem, like an input or output not working as expected, one could reverse engineer the pinout, trace back to the components, but ultimately that's a shit-job without a schematic and a test mode. If it's simply Dead, your option is to run down the input power sections, but any kind of board-level troubleshooting approaches diminished returns quickly.

    '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!

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