Reverse polarity light

[ghost0070]

Like most At 34s I have a reverse polarity light on the shore power 1 AC panel. It was a red light so off was good.

With the boat out of water, I plugged into a standard outlet with a #16 extension cord, turn on AC power, and the light stayed off. I then turned on the salon strip heater, pulling about 10 amps and the light came on. Used a multimeter and apparently the shipyard outlet is wired correctly. Other times I plugged into a standard marine outlet with a 30 amp power cord and the light stayed off. Why is the light coming on now?

 

[Comodave]

I bought a 15 amp to 30 amp adapter (Marinco) and it was wired incorrectly and had neutral and ground switched inside the molded adapter. Sent it back and got a new one and it was ok. Check your adapter and extension cord and make sure they are wired correctly.

 

[sdowney717]

Maybe the salon strip heater has a ground fault. If it does and you use a GFCI extension cord, turning on the heater it will trip.
But if it is only coming on when using that plug, maybe that plug has a problem.

For that light to come on, power has to be flowing on the ground wire, and returning by way of the neutral, hence a ground fault exists causing the light to some on. The reverse polarity light is typically a tiny red neon bulb set between ground and neutral wires.

 

[Duvie]

Just thinking out load.

Possibly if there were a poor connection or very long/under sized feed within the supplying neutral. This would cause a potential difference between ground and the neutral. The potential difference would rise as the current draw increases. That is why the light comes on as the current is increased by the strip heater.

Check voltage at the strip heater with it turned on. Check line to neutral and line to ground with the heater on. Guessing you may see a significant difference.