Boondocking - power transfer switch (DC to AC ) quit working

Having a MULTIMETER around is very helpful determining if your batteries are charging.

I use my MULTIMETER all the time across the battery terminals to check their DC VOLT level. If they are 'fully charged' I see from 12.6-7VDC when my trailer is not connected to the shore power or AC Generator. When I connect to shore power or attach a Generator the DC VOLT LEVEL will jump up to 13.6VDC or higher telling me the battery is charging. Same thing should happen for your batteries.