AC Electrical Troubles

Was this while you were connected to shore power? Most times I've seen this it's been because the shore power plug was lose or there was a problem at the pedistal.

+1 on this...had the same thing happen this past winter on my 3807 as we were restoring it.....was loose power cables every time, finally scorched them enough to ruin them. I had the boat connectors re-wired from the OEM 50 amps, which required adapters, which were always loose and falling out, to 30 amp connectors so I could eliminate the adapters, and no more loose cords, no more reverse polarity lights.

First check that your connection to the outlets is solid (boat end as well). Often the outlets are damaged by people who forget to give that 1/8" turn to the right after plugging in. If that doesn't do it try another pedestal. If your connection remains lose you may be able to tighten it by bending the prongs just slightly.

Check the power source

We had a similar issue last year after the marina was rewired.

Try using a cable known to work for someone else then check your power source.

If no change try plugging into a different power pedestal using the good power cord. Good luck

First I'd use a small wire brush to make sure there's no 'green' corrosion over any of the shore power connecting metal which is a good idea to do routinely anyway to keep heat from building up. If the shore power connector is home made [replaced plug etc] make sure it's wired correctly. Secondly if you have an adapter to go from the marina's stanchion, to your shore power cable, adapted to ordinary 120VAC wall power, you can use one of those small outlet testers to see whether the marina is wired correctly. If you're good with a voltage tester, you can do it manually at the stanchion testing that hot is not swapped for neutral. If all wiring checks out correctly to the panel, then I'd check that no shorts exist between the panel and each leg going to the A/C ; it's more work, but the process of elimination.

Do you happen to have a voltage isolator on your boat? That would explain why the ground was taken off the plug or disconnected. First time I ran into that I thought the leg had broken off. The boat yard was about to install one for us. Fortunately I spoke with the mechanic as he was doing the job. He was installing it because it was ordered, but didn't understand why since it wasn't supposed to be there. I got educated.

If it's working when connected that's right. If you had an isolator the line would ground on the boat, not at the pedestal, thereby eliminating the need for a grounded plug.