RV Repair: power convertor, 12 volt batteries, magnetek

Question
I have a older Magnetek power convertor w/battery charger. series 8300A model 8345.

How do I tell if charger is producing when hook to shore line.
Seems lately that when shoreline disconnected that 12 volt system for lights etc aren't working.

The 2 12 volt batteries are a year old.

Answer
Hi John:
When the unit is plugged in the battery voltage should jump to about 14 Volts. Then when you unplug it drops to 12.5 or so eventually getting to 12 if the batteries are fully charged. Hook a volmeter to them and check while somebody plugs it in to shore power. Obviously the converter is working cause you have DC when you plug in. Check to see if there is a breaker or resetable circuit breaker in the charging wires to the batteries.
Bill