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Unfortunately, establishing a good ground is a bit more complicated than tightening down all connections. And creating a ground system at a residence that is anywhere close to 5 Ohms isn't practical. That spec for <5 Ohms is for things like communications sites, like cell towers, and typically costs thousands of dollars to achieve.Yes, the car doesn't like when you have too much resistance between ground and neutral. IEEE recommends <5 Ohms. Here is a good article about this.
The reason is obviously that sitting on isolating rubber tires and without a low resistance ground connection, even a minute leakage current from the charge voltage can make the car dangerous to touch, so you are lucky that the car gives you a warning.
To be safe you should measure your local ground connection. To make the car happy, all you need to do is tighten down your neutral and grounding conductors/conduits from the outlet all the way up to where they bond in the service panel, until you have 0 ohm between them. Theoretically you could still get shocked but the car will charge since it can't know what "real" ground is. I don't condone that as a sole measure though.
Are those garage plugs on a subpanel? Your description makes me think perhaps neutral and ground have been bonded together somewhere they shouldn't be, like in the subpanel. I suppose it could be in one of the electical boxes as well. Ground and neutral should only be connected together at the main service panel. If it's done anywhere else, it can cause the ground to have return voltages on it. Another way this can happen is inside an appliance either because of a broken/worn wire, or because someone tried to repair or replace a power cord and wired it wrong. It also happens if a homeowner installs a light fixture incorrectly.I used one of those plugs to check if grounding/hot/neutral are correct.
Interesting that I’m finding that when I open/close the garage door the light for ground goes from bright to dim. I was seeing lower voltage warnings at 12 amps when opening the garage but lowered amps and have not seen problems since.
With the Tesla plugged in I am often seen the ground light completely go off and on but it’s random. Sometimes flashes, sometimes always on, sometimes always off. At one point I did see the ground/neutral switched light come on but that was just for a short period.
I got shocked from the light switch out there in the summer. I had an electrician come out and look at it and all he did was changing the light switch. He said it was old and close to the conduit but that he didn’t sound like it was 100% what caused it.
I can have the electrician out again at some point but trying to save some $ after my Tesla purchase. My biggest concern is safety. It’s seems like the Tesla is smart enough to stop charging if there is an issue. That doesn’t bother me. I just want to make sure it’s safe.
I work from home so mainly drive it on the weekend. It’s just sitting in the garage at about 70-80% charge. I’m happy to just leave it there until the weekend but I know people recommend keeping it plugged in when not used, especially since the weather is getting cold in Chicago.
I don't think you read this part:Unfortunately, establishing a good ground is a bit more complicated than tightening down all connections.
Theoretically you could still get shocked but the car will charge since it can't know what "real" ground is. I don't condone that as a sole measure
Correct, you can't get absolute zero. You should get 0 but probably not 0.1 if we are thinking in significant digits, where 0 means <.5 and 0.1 means <.05 and so on.And sorry, no, measuring for zero Ohms isn't going to be helpful. All circuits have resistance. You can do things to lower it (like sinking that second ground rod), but you can never get it to zero.
I know. We are not testing ground quality in that picture, but testing for resistance of neutral and grounding conductors since there was no continuity before the repair of our service panel.@Olle, you can't test the quality of a ground system with a multimeter.