Does the battery charge when the trailer is hooked to a.c. ? Have a 2015 timberidge. 2nd question there is a switch on the panel labeled solar on top power on bottom. What does it do?

The battery automatically starts charging as soon as shore power is connected to the unit if you used a volt meter and measured the battery voltage at the battery posts and then plugged the unit in and measured voltage you would see the difference in voltages which should be over 13.3 volts roughly you could confirm that your converter is doing its job and give yourself peace of mind

Yes it changes when you are plugged in. The solar switch turns on the small solar panel so it can trickle charge your battery.