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Slow Charging Speed question

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I have put a 50amp breaker in the garage, 240 outlet, the onboard is set to 40amp. I used to get 28, 29 miles per hour charging, but the last few days its only been 12-14. Am I doing something wrong? Software is still the .42 version. And the Tesla App won’t always connect to my car. Thanks in advance
 
Check the breaker and the outlet. Sounds like one of the two hot leads has disconnected, so now you're getting 40A at 120V.

It doesn’t work like this. It gets 240 volts across the two hots. If one is disconnnect then there will be no power at all.

As far as the original question goes, I would look at the amount of power the far says that it’s getting rather than miles per hour. Is it showing that you’re charging at 40 amps? Is it possible that somehow it got turned down for that location?
 
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It doesn’t work like this. It gets 240 volts across the two hots. If one is disconnnect then there will be no power at all.

Actually, I take this back. Sort of. When I posted that I was thinking of the HPWC, which doesn’t even have a neutral connection and will charge at 240V or nothing. However, the OP didn’t say what he was using to charge with. If he’s just using a 14-50 outlet with the mobile connector then I don’t know how that would handle the loss of one of the hots. The mobile connector can charge at 120 or 240 volts, and a 14-50 outlet does include the neutral, but I don’t know if the neutral is even wired through the mobile connector’s 14-50 plug or if it would use it to charge at 120V if it only had one hot. So I guess this might be possible. Maybe.
 
Actually, I take this back. Sort of. When I posted that I was thinking of the HPWC, which doesn’t even have a neutral connection and will charge at 240V or nothing. However, the OP didn’t say what he was using to charge with. If he’s just using a 14-50 outlet with the mobile connector then I don’t know how that would handle the loss of one of the hots. The mobile connector can charge at 120 or 240 volts, and a 14-50 outlet does include the neutral, but I don’t know if the neutral is even wired through the mobile connector’s 14-50 plug or if it would use it to charge at 120V if it only had one hot. So I guess this might be possible. Maybe.
I am using the mobile connector with the 14-50 outlet. It was doing great until I plugged it in today.
 
Something almost definitely finicky with the outlet or breaker wiring. If you can flip the breaker then it will be perfectly safe to check the receptacle's wiring without risk of frying. For most setups it's easy access (a few screws) and easy wiring (leads into contacts, screwed down tightly). If you're not comfortable with it, I understand, but it's not difficult or unsafe.

You can also pick up a cheap voltage tester and stick it in the slots to check for current. Both the left and right should have current.
 
Something almost definitely finicky with the outlet or breaker wiring. If you can flip the breaker then it will be perfectly safe to check the receptacle's wiring without risk of frying. For most setups it's easy access (a few screws) and easy wiring (leads into contacts, screwed down tightly). If you're not comfortable with it, I understand, but it's not difficult or unsafe.

You can also pick up a cheap voltage tester and stick it in the slots to check for current. Both the left and right should have current.
Thanks, I will try this