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Problem charging at 110V on Tesla UMC (Red T)

Came up to my parents' cabin with my Model 3 (first road trip!). I was hoping to charge the car using a standard 110V outlet and the Tesla provided UMC (universal mobile charger). When I plug in the UMC, the TESLA letters light up green, but when i plug the UMC into the car, I hear some clicking noises, the T on the UMC turns red and the car does not charge.

I have successfully used the UMC at 110V at two other locations, so I'm pretty sure the UMC itself is fine. I'm planning to upgrade the cabin's power service this summer and install a NEMA 14/50. But any guesses as to what's going on?

My engineer brother thinks the cabin wiring is likely to blame. Maybe common and ground are connected? The wiring is 70 years old, so I wouldn't be surprised. But we haven't had issues running any appliances or basic 110V chargers (like traditional lead acid car battery chargers). Just curious if anyone has any ideas/suggestions.

Thanks,

-Chris
 

jerry33

(S85-3/2/13 traded in) X LR: F2611##-3/27/20
Supporting Member
Mar 8, 2012
20,356
26,791
Texas
The best solution is to get your electrician to run a 50 amp NEMA 14-50 (aka RV plug). This isn't particularly expensive, and charges much faster than a 120V outlet. It's also probably less expensive than correcting the wiring.
 

swaltner

Active Member
Oct 13, 2012
1,711
1,812
Kansas, USA
Yep, there’s probably something wonky(tm) with the outlet. Test it with something like https://www.amazon.com/dp/B008E07HM2/ which you can find at a local hardware store as well as on-line. These devices test for swapped hot/neutral, bad grounds, etc... Some, like the one linked, can even test trigger the GFCI breaker. I don’t know if you can really test for neutral and ground being swapped.

70 year old wiring: if I had to guess, someone did an invalid outlet swap in the past and it’s a floating ground (not connected). That or the wiring isn’t up to snuff and the voltage sags so much when it tries to draw current that the car is afraid to charge from the outlet.
 

scaesare

Well-Known Member
Mar 14, 2013
8,642
15,405
NoVA
You use a multi-meter for testing those.
Agreed.

In addition, I actually bought this set of testers which includes a voltage sniffer that you can use to at least see of you have voltage on the individual leg(s) of other receptacle types.

While it doesn't provide the same Info a multimeter will, it's useful to at least determine if an outlet even is alive...
 
You use a multi-meter for testing those.

Thanks, tracked down the one I used a long time ago to fix my Atari 2600. Didn't appear to work for my outlets, though it worked on batteries just fine. Have no idea where the manual is, and didn't have any luck finding a copy online. Finally figured out I needed to hit the SELECT button to turn on the ~ indicator, which I gather indicates testing for AC rather than DC.
 
Yep, there’s probably something wonky(tm) with the outlet. Test it with something like https://www.amazon.com/dp/B008E07HM2/ which you can find at a local hardware store as well as on-line. These devices test for swapped hot/neutral, bad grounds, etc... Some, like the one linked, can even test trigger the GFCI breaker. I don’t know if you can really test for neutral and ground being swapped.

70 year old wiring: if I had to guess, someone did an invalid outlet swap in the past and it’s a floating ground (not connected). That or the wiring isn’t up to snuff and the voltage sags so much when it tries to draw current that the car is afraid to charge from the outlet.
Nice. I'll check that out. As I mentioned, I was planning on having an electrician come out anyway to upgrade the service to 100A or 150A, replace the ancient fuse box with a new breaker box and probably put in a sub-panel in the shed near the driveway. This way I'll be able to put in an HPWC or a NEMA 14/50 in the shed close to where the car is parked.

When he redoes the box and upgrades the service, I'm sure the electrician will wire everything properly. I think there are only a total of 7 or 8 outlets in the whole cabin, so I might just bite the bullet and rewire all of them from the new box.

Thanks for the tips.

-Chris
 
You should also invest in a 12 gauge extension cord if you plan on plugging into 110v sockets that are out of reach for the UMC.
I did. I use that for an electric chainsaw (same outlet that I tried to use to charge the car). Works great for the saw, but not the car.

I actually tested two different outlets and 3 different extension cords with the same results. So either the house wiring isn't up to the current that the car wants to draw (10 amps?) or there is a ground fault of some kind, or some other flaw with the wiring. The fact that the TESLA logo lights up green on the UMC but then goes to the red T when I try to actually charge the car suggests to me that it might be an insufficient current problem. But what do I know? I'm a liberal arts graduate. :)
 

Rocky_H

Well-Known Member
Feb 19, 2015
7,851
9,878
Boise, ID
If it were a ground fault, the mobile charge cable usually tests for that and will show an error before you ever plug it into the car. I had that at a friend's house, where they have little outlet posts along their driveway. Apparently the ground was never done right on those, so the UMC just kept showing red.
 

ThosEM

Space Weatherman
Dec 13, 2013
870
324
Annapolis, MD
I’m having this very problem at a home I’m visiting where I previously did not have the problem at all. No wiring changes have been made at this home that could account for it, to my knowledge, Two different outlets show the same behavior, one with a GFCB and one without. Turning down the current from 12A seems to delay the eventual cutoff, but it happens even at 8A.

It seems like the UMC has gotten more sensitive to whatever it is using as an indicator. Very annoying to have trouble at such a low power level at a location where this was never before an issue!

985179E0-EFC7-479E-8A5A-AB000235F5CE.jpeg
 

Rocky_H

Well-Known Member
Feb 19, 2015
7,851
9,878
Boise, ID
It seems like the UMC has gotten more sensitive to whatever it is using as an indicator.
I don't know that I would expect that it's the UMC which is getting more sensitive. I would think more likely, the GFCI has degraded more and is finally bad enough to have that problem.

Now you said one with a ground fault circuit breaker and one without. Are these outlets on the same circuit, though, like in the same room? Because one GFCI outlet covers the whole circuit including all the other outlets.
 
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eprosenx

Active Member
May 30, 2018
2,076
2,554
Beaverton, OR
I did. I use that for an electric chainsaw (same outlet that I tried to use to charge the car). Works great for the saw, but not the car.

I actually tested two different outlets and 3 different extension cords with the same results. So either the house wiring isn't up to the current that the car wants to draw (10 amps?) or there is a ground fault of some kind, or some other flaw with the wiring. The fact that the TESLA logo lights up green on the UMC but then goes to the red T when I try to actually charge the car suggests to me that it might be an insufficient current problem. But what do I know? I'm a liberal arts graduate. :)

It sounds like one possibility is that the ground is either not connected properly or ground and neutral are not properly bonded at the panel. The UMC will detect these conditions and refuse to allow power to flow.

Test with a “circuit mouse” (tester with three lights) or better yet with a multimeter to check voltages.

A bad ground won’t stop most things from working, it just makes them unsafe if something bad happens. What makes an EVSE like the UMC unique is that it tests for dangerous conditions and just refuses to operate if a safety hazard exists.

The industry has doubled down on safety since they don’t need the bad press. :)
 

ThosEM

Space Weatherman
Dec 13, 2013
870
324
Annapolis, MD
Well, the rain has ended and I’ve read the UMC gen2 guide, and normal operation has resumed, so I conclude that this UMC is much more sensitive to moisture than I would have expected. The manual does express cautions about wetting of the cable or connectors...

I’m having this very problem at a home I’m visiting where I previously did not have the problem at all. No wiring changes have been made at this home that could account for it, to my knowledge, Two different outlets show the same behavior, one with a GFCB and one without. Turning down the current from 12A seems to delay the eventual cutoff, but it happens even at 8A.

It seems like the UMC has gotten more sensitive to whatever it is using as an indicator. Very annoying to have trouble at such a low power level at a location where this was never before an issue!

View attachment 338935
 

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