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Discussion Starter · #1 · (Edited)
I don't remember seeing this fix before, posted here today THANKS TO @MDMTahiti

He had previously checked for over 11.5V at the starter battery terminals, but it wouldn't start. He was plugging into a freshly rebooted OEM cord, but it wouldn't charge. Plugged in or with the key turned even one click, voltage should have been over 14V if the contactors were connecting....:

12V was at 12.12V key off, and 11.81V key MAR
.... I did not hear the "Clunk". I decided that the contactors were not engaged, so the system did not "see" the charger, but sensed the plug in the socket. In OBD I went to battery management and selected enable contactors and suddenly everything is right in the world. The car is 100% working.
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(final pic also by @MDMTahiti )
 

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Should also read this post:

 

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Discussion Starter · #3 ·
Ya, & summarizing that one chronologically:
  • AlfaOBD paid version wouldn't connect to Konnwei OBD dongle with yellow adapter.
  • Without adapter it worked as usual ("battery management" only).
  • Resting a day or more the 2016's 12V starter battery died so the car wouldn't start or charge.
  • Replaced 12V & it still wouldn't start or charge (no "clunk").
  • Disconnected humidity sensor but it still wouldn't work.
  • Enabled Contactors in OBD & it's fine.


Others here have reported contactors suddenly not activating for some reason, even with enough % & a good 12V. I believe every single time it was after resting overnight. This might be something to try when that happens.
 

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Certainly makes one wonder. It would be interesting to know what ways the contactor can get tripped from enabled to disabled. The fact that it is even an option makes me wonder about how many of those reports of no longer hearing the clunk are related to this.

It is interesting (to me at least) that following this and other 500e forums for the past few years, this is the first time I've seen this.
 

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Discussion Starter · #5 ·
100% agreed.

The humidity sensor has been reported to disable ABS, Cruise, ESC, HSA, PRND, RBS, & SRS (airbag). Maybe it can also disable the contactors! THAT glitch might require re-enabling them with OBD, as above.

I was already wondering why every single report I can recall of supposed "failure" of the HV pack happens overnight* :unsure: .

NOW I wonder if some/all of those were just contactors disabled by another glitch that dealerships don't know about: We get drive system glitches, fixed just by key off/on, charge glitches fixed just by plugging in the OEM cord, & other glitches fixed by 30-second 12V disconnect.


* Aside from ONE report I remember, from EUROPE, where I think a cell died while driving, due to extended storage unplugged during transport.
 

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I really think I was the cause of the contactors being disabled. I may have started the HV Isolation test by accident, and that would have disabled the contactors. Otherwise, the car as worked perfectly for the past year.

Chalk this up for experience - and hopefully it will help others. AlphaOBD and the dongle can cause problems. There are lots of options/modules/tests on the paid AlfaOBD that do not appear on the demo version. This all started because I was trying to hunt down a way to set the time and date without the OEM radio (2016 500e).

Thanks again to Electric Tire Shredder for all the help!
 

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Discussion Starter · #7 ·
Thank YOU for discovering this possibly game-changing fix. I'm trying to compose another new post about that. Meanwhile...:

While I agree it COULD have been user error, it seems just as likely to be a glitch, possibly from the humidity sensor, or from letting the 12V drop below its functioning threshold.

Another user's car failed before he even got OBD. He got it, used it to
reset the contactors, & the car worked:

 

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Discussion Starter · #8 ·
There have now already been FOUR reports of this fix working!

Turns out it is NOT caused by the humidity sensor, which is a bit unfortunate since it means we can't avoid it just by leaving the sensor unplugged.

I upgraded post #1 above with pics showing the entire sequence.
 

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I noticed that on AlfaOBD that it was reporting an error code on my disconnected humidity sensor. Small potatoes...
 
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