My 88 carver 3607 comes with 4 batteries. One for engine starting one for generator starting and two large 4D house batteries. One is reading 13 volts the other 9. I have the switch in the closet to go from battery one to two to all. My norcold fridge works on shore power but very recently will not turn on from house batteries. The light is green and faint and pulses slightly which means it’s getting some power not enough to get cold
I have switched back and forth between batteries and set it to the “all” setting and still nothing. I am replacing the one 4d house battery tomorrow. Any suggestions on why fridge acts like it wants to work?

As a side not I read people watching tv and things off of house batteries. Mine power cabin lights water pump and used to be fridge. No plugs no tv obviously no ac. Is this normal ? Thanks for any thoughts.