Yes I'm a Chinook newbee but I have tinkered and troubleshot mechanical & electrical stuff for over 50 years.
That said, I have a need to what is normal with the Magnatek charger when shore power is connected.
Has anybody measured the input voltage to OEM coach light fixtures when shore power is connected? I just did (as I was troubleshooting my recently "FRIED" OEM 21" florescent ballast and much to my surprise, the input voltage at the switch was 17.3 volts DC. WOWZER.
The florescent tubes worked fine for many moon but I installed proper 4000K LED tubes last night and left them on for an hour ... thats when the bad smelly thing happened.

But the good news is, when I flip off the circuit breaker or my shore power is removed, voltage drops to 12.6 VDC.
The big question is:
Is 17+ VDC input voltage (while on shore power) normal for this rig? Or am I needing to dive into the charger ??