Originally Posted by WaltW
rgolding, but humming all the time? I am plugged in, 12V switch off, and it's humming. I would think it would stop running sometime. Chassis batteries may have some load but they are not connected to the house batteries via charger/converter.
Did you try shutting off the "converter" breaker while plugged in to shore power to see if that made noise stop? That will take the converter offline but the transfer switch will be unaffected.
Doing that is the only thing that stops my Seneca's humming, my transfer switch is quiet. It gets louder as I add 12-volt loads. After running for a while with high loads the cooling fans eventually kick in.