Battery & Wiring Question

[NorthPuffin]

I bought a new-to-me 2009 XT245 toy hauler and found that the battery isn't charging when the trailer is connected to the tow vehicle. I haven't yet plugged the trailer in to 120VAC so I don't know if it charges on the converter.

Everything 12V (lights, water pump, refrigerator, etc) works fine when the trailer is connected to the tow vehicle. Nothing works when not connected to the tow vehicle. The battery voltage is very low (7.2V) so the 12V gear may not work anyway. The battery disconnect switch has no effect on the 12V appliances.

I disconnected the battery cables from the battery and measured the voltage across the cable terminals: Read 0 volts with the battery disconnect switch pushed in and 0 volts with the disconnect switch pulled out.

This problem could be a bad switch, a broken wire, or something I haven't thought of. I'd appreciate ideas.

Mostly, I need to figure out the circuit. Is there a wiring diagram for these toy haulers posted anywhere?