I'm seconding
@stopcrazypp about what, "3 pin" connector you're referring to.
First off: A standard
NEMA5-15 (that's your standard 120 VAC, 15A socket used in the US & Canada) is typically installed on a 15A, 120VAC circuit. National Electric Code states that such a circuit shall not, with a continuous heavy load (hello, Tesla!) be run at over 80% of the circuit rating. Take my word on it: This is for good, don't burn the house down reasons.
The Tesla Mobile Connector and the car respect that limit, so, when plugged into a NEMA5-15 socket, one would be expected to see 12A (80% of 15A). Yet.. you said 10A. That's decidedly odd. I have charged on such a socket and, yeah, 12A is what I get.
Now, there's a couple of reasons that a Tesla won't charge at 12A on a NEMA5-15. First off, there's a temperature sensor built into the NEMA5-15 adapter. If it riseth up, the car's software thinks that there's something Wrong and, to Save The Day, will reduce the current draw. Since power dissipation goes as the square of the current, going from 12A to 10A reduces the heat being generated by (12/10)^2 = 1.4 times. So, is that happening? Is the plug distinctly warm?
The other reason is that a Tesla monitors the voltage drop going into the car. The presumed algorithm is to sample the voltage at the car with no current being drawn, then monitor the voltage as the current goes up. If the voltage drops too much, the argument is that there's a loose connection out there, not necessarily at the socket. Loose connections create heat, lots of it, so, again, in the interests of No House Fires, Tesla will reduce the current. (This also has the side effect that, if one is using a cheapie extension cord with tiny wires, the voltage drop across the extension cord is enough to trigger this action. There might be no danger of a fire in this instance, but better safe than sorry.)
The point I'm making here is, if that 10A crack you made is accurate, you may be currently risking a house fire. You implied that this was an outside-the-house socket whose health you were doubting. THIS WOULD BE THE TIME TO REPLACE THAT SUCKER, sooner than later. Do it this weekend, don't futz around. And use an outdoor-rated socket when you do it, too.
If you continue to see that 10A number, it's time to Stop Charging with that setup and call an electrician.
On that.. I happen to be electrically cognizant and, in such a case, I'd be running around, removing the panel on the breaker box, measuring voltages and voltage drops, and figuring out where the trouble was. I note that breakers have been known to die as well as sockets. But if some mouse has been chewing on insulation somewhere, the problem could be anywhere. If you're not up to that kind of speed, don't mess around: Call an electrician and get their take on it.
One last bit. I, personally, have seen a standard NEMA5-15 wall socket explode with flames and all, at which point the breaker popped. NEMA5-15's are typically made of plastic insulators with metal inserts for the contacts, screws, braces, and what-all. The problem with worn-out contacts (which will eventually happen) is that they get
hot when current goes through them. It might not be hot enough to actually make the socket catch on fire, but it can get warm enough to accelerate the natural ageing process on that plastic in there. And, once the plastic gets old enough, it can crack and collapse.
In such a case, if one is
lucky, one will get an open (which is ok for safety, at least the thing isn't going to explode), or a dead short good enough to pop the breaker (which is also good for safety), but there's always the possibility that one will get one of those nifty "incidental contact" situations, where there enough current flowing to set the wood of the house on fire, but not enough to pop the breaker. Standards makers and socket manufacturers like the first and second scenarios and hate the last, so they do try to make sockets that will fail safe. But that's an aspiration, not a guarantee.
