UMC No Power with Nema 14-30

[inigopark]

Hello, This is my first posting, but very urgent for me.
I have Model 3, two weeks old.
I’m using Nema 10-30 dryer outlet and Tesla adaptor. UMC worked first week without any issue but it stops working from last week. I still could charge with Nema 5-15 (110V). I measured the Nema 10-30 outlet and it shows around 110V. Dryer also not working. UMC doesn’t show any lights.
So, I replaced circuit breaker and outlet to Nema 14-30, and dryer is working now, but UMC still doesn’t show any lights.
This is measurement with Nema 14-30 outlet itself:
- Red+Black: 220V
- Red+Neutral: 120V
- Black+ Neutral: 106-108V

This is measurement with Nema 14-30 outlet with UMC plugged:
- Red+Black: 4V
- Red+Neutral: 121V
- Black+ Neutral: 118V

Tesla Mobile Service came this morning, and tried a new UMC, but still have no clue yet.
Please help me what could be an issue here.

Thanks,
Inigo

 

[Dmagyar]

Call a genuine Electrician to check your problem, red-black voltage should be 240 volts, black-neutral 120 volts, red-neutral 120 volts. If the tesla service came out and didn’t find a faulty UMC, problem has to be wiring/breaker/panel/utility supply.

 

[DaveRZ]

Electrician time! You sound like a DIYer, as am I, but there's a time to bow out for safety's sake and I'd say this is it.

That being said, your dryer working on that circuit is probably not a good test unless you verified you are able to dry clothes with it. Meaning, the electronics and drum motor probably run on 120v (which you have from red + neutral), but the heating element will run off 240v (red + black), and that's where you're broken.

(hire an electrician)

If you want to continue to troubleshoot, here's how I would do it as a DIYer with no official electrical training: I'd start by making sure your other 240v appliances work (assuming you have an electric oven or A/C). This will indicate you have workable power from your utility company.

(hire an electrician)

with the UMC still plugged in, I would test voltage coming out of the breaker to see if you're also seeing the same voltage as you do at the outlet, or if its normal (e.g., 120v from each leg to neutral/ground, 240v across both legs). If the voltage is low at the breaker, then its either a bad breaker or a problem in the panel like a damaged bus bar. If the voltage is normal at the breaker, then you likely have a problem in your wires or connection at the outlet

(last time: hire an electrician)

good luck.

 

[Dmagyar]

last time: hire an electrician)

Love this...after purchasing a $60,000 car +- that’s the only sound advice to get this fixed.

 

[brkaus]

How did you swap out a 10-30 to a 14-30? Was there an unused ground wire run to the outlet location?

edit - sorry - typo. I changed to ground.

 

[AltLogic]

Are you certain of the 220v at the outlet at the present time? If so, the voltage shouldn’t drop to 4v with your UMC plugged in (without a car plugged in to the other end) unless you have some serious problems that require electrician level skills.

4v hot to hot and ~120v individual hots to neutral (or ground) sounds like both of your hots are on the same leg and you have a cheap voltmeter or the above serious issue.

 

[inigopark]

Update: I found the issue and fixed it. There was a junction box in the attic and it was burnt, short the black and ground wire. After cleanup and fix it, everything is perfectly working now. Thanks for all the comments.

 

[640k]

Update: I found the issue and fixed it. There was a junction box in the attic and it was burnt, short the black and ground wire. After cleanup and fix it, everything is perfectly working now. Thanks for all the comments.

uh...

 

[DaveRZ]

Update: I found the issue and fixed it. There was a junction box in the attic and it was burnt, short the black and ground wire. After cleanup and fix it, everything is perfectly working now. Thanks for all the comments.

I'm glad to hear you got it working! However, I'm somewhat terrified regarding the problem you found and all the questions it raises. Not to mention that potential wiring damage could be hidden elsewhere if you had a dead-short, then things were cooked enough to not pop the new breaker.

Remember that charging an EV takes a much higher amount of power than your dryer does, and as a continuous load (unlike your dryer that will cycle on/off for heating). This means that wiring can easily overheat if things aren't done correctly.

I would once again highly recommend that you hire an electrician to inspect everything.