I suggest you disconnect your MH from shore power. Then, clean and tighten all connections from converter to batteries. Pay special attention to battery terminals. There is most likely a circuit breaker just before the charge wire gets to the batteries. Check this circuit breaker closely for no resistance, or replace it. Also make sure minus (ground) battery cables to frame connections are clean. If there is corrosion at the end of the battery cables inside the connection terminals, it will cause high resistance and should be replaced with new cables.
If you have a battery that is bad, you could get a low reading at the battery.
If you still have the original Magnetek converter your MH came with, it should be replaced with a modern multi-stage charger like the Progressive Dynamic models. The Magnetek converters are prone to overcharging the batteries and having bad filter capacitors in them. Make sure your batteries are always topped off with distilled water. The Magnetek converters are notorious for boiling out the water and making dry batteries that then kils them.
Good luck-- Mick
2007 Itasca Suncruiser 35L
2000 Jeep Wrangler