time2roll wrote:
I assume it measures voltage between the hots and with a 30a adapter you have zero volts measured but power s/b fine.
The 30 amp plug provides power to both hot legs otherwise only half of the trailer would have power when at a 30amp pedestal. I have a hard wired PI surge protector and I show 120 on both legs. Sure you still only have 30amps total to the whole trailer.
When mine went out and I was hooked up to my 30amp at my house (have 50amp also but no reason to use it when just plugged in to charge the batteries) after changing it out had blue lamp. The blue just look to see if power is available not voltage on both legs.