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UMC2 handle won't latch

jgs

Active Member
Oct 28, 2014
1,581
933
Ann Arbor, Michigan
I normally charge my early 2015 Model S using the original-version 40A UMC that came with it. But, that one is out of commission for a while ever since the NEMA 14-50 outlet I had it plugged into melted down. At least it didn't catch on fire, quite, though it was only dumb luck that I happened to be home and notice the smell of smoke. :eek: The UMC itself appears undamaged and energizes when I plug it into a household outlet but I'm unwilling to reuse the 14-50 plug end that was in the line of fire. It has plastic melted all over it and charring on one of the pins where it was presumably arcing. I've ordered a new one but it won't arrive until Friday.

For that matter, I'm a bit concerned this could even happen, in general my experience has been that the car senses when something is even a little out of whack with the power it's plugged into and won't charge at all in such cases, I've experienced that when plugging into improperly-grounded household outlets at vacation rentals for example. But this time it kept happily drawing 40A long enough to straight-up melt the outlet. I'll post a pic later if I get a chance.

But that is all beside the point, or anyway just background, to my question. Since my UMC1 is on the shelf until I get my replacement plug, I'm using the UMC2 we got with my wife's Model 3. I've used it before successfully, but now when I plug it in to my Model S, I cannot for the life of me get it to latch. I hear the latch trying to engage and giving up. Since it's not latched, it won't dial the charge rate up to the full 32A, and I'm limping along with 16A charging. I'm pretty sure the latch is OK, since while I was waiting for the outlet to be fixed I was charging at the local Supercharger and that was fine.

My question, after all that, is whether failure-to-latch is a well known problem with a well known fix, and if so, what is it? TIA.

(As an aside, this is an interesting-to-me example of the single point of failure being different from what people assume it will be. I've participated in a number of discussions over the years where people say they're getting a backup UMC because they're afraid their UMC will break leaving them unable to charge. I had two UMCs... but my outlet broke.)
 

Rocky_H

Well-Known Member
Feb 19, 2015
5,990
6,906
Boise, ID
but I'm unwilling to reuse the 14-50 plug end that was in the line of fire. It has plastic melted all over it and charring on one of the pins where it was presumably arcing. I've ordered a new one but it won't arrive until Friday.
Yes, I wouldn't use that old one. This is a nice thing about the changes they did with the 2nd generation mobile connector. The plug ends have temperature sensors in them, so if your outlet was overheating and melting and charring things, it will throw a big fat warning in the car and interrupt charging.

but now when I plug it in to my Model S, I cannot for the life of me get it to latch. I hear the latch trying to engage and giving up.
Yes, I've heard of this one a time or two, but I can't get my Google-fu to locate the threads on it here. Usually this is just a bit of unfortunate variation in manufacturing tolerances in the plastic of the handle. There is that cut out notch in the bottom of the charge handle, and the pin in the charge port that is trying to push up into that space isn't quite lined up right, and is catching the edge. That is sometimes showing up from the handle fit in the port being a little tight, so it stops short unless you really use some force to shove it in. But people have been able to fix that by widening that notch just a little bit by grinding at the back edge, like a millimeter, with a Dremmel tool or something, so it has enough space for the locking pin to fit in the opening and not catch that edge.
 
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jgs

Active Member
Oct 28, 2014
1,581
933
Ann Arbor, Michigan
That is sometimes showing up from the handle fit in the port being a little tight, so it stops short unless you really use some force to shove it in.
The UMC2 handle is definitely snug. I've considered putting some silicone grease on it, but overall it didn't seem like a prudent thing to do. I don't have a caliper to check it with, but using good old stare-and-compare it sure looks as though the notches are in the same place -- but I guess if the handle doesn't go in quite as far, it's as good as the notch being positioned wrong.

The weird thing is this didn't happen over the summer. I suppose there may be just enough shrinkage from cold weather that a handle that was marginal is now below-margin.
 

KArnold

Member
May 21, 2017
514
496
Columbus OH
I have a backup gen 2 UMC for my MS. Using my regular "push the handle in" motion, it won't latch more often than it does. I discovered that slight downward pressure on the handle while fully inserted will consistently latch. Of course, YMMV.

Also, I leave my Gen 1 UMC always plugged into the 14-50 at home. I don't want the strain that plugging in every day would do.
 
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jgs

Active Member
Oct 28, 2014
1,581
933
Ann Arbor, Michigan
I have a backup gen 2 UMC for my MS. Using my regular "push the handle in" motion, it won't latch more often than it does. I discovered that slight downward pressure on the handle while fully inserted will consistently latch. Of course, YMMV.
Thanks. Perversely, after my car finally finished charging at 16A, when I went out to unplug and move it (so my wife could charge) I found the handle had finally engaged. Go figure.

Also, I leave my Gen 1 UMC always plugged into the 14-50 at home. I don't want the strain that plugging in every day would do.
Me too. The one that melted had been plugged in for months. I guess maybe the lesson is leave it in, but check it occasionally. Or just, "don't have bad luck"?
 

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