Electrical problem

My coach batteries are not being charged by my chassis battery. (They are being charged when connected to a 120v electrical system.) Fuses and inverter are apparently OK. Any suggestions where I should look next to trouble shoot this problem?

Replying here to my own question in case anyone else encounters this problem. There was a blown fuse in the circuit preventing the aux batteries from charging. That fuse in my 2009 Fleetwood Pulse 24D is located under the driver's seat (not in any of the fuse boxes). It took an electrical mechanic about 4 hours to track down the problem, find and replace the fuse. So if this happens to you, check the fuse under the seat.

Do you know the fuse #. All my 12 volt systems went out early in the am today. Woke to a high pitch alarm while plugged into shore power. If I start the engine everything works again. HELP please ( new owner 2010 pulse). Thanks in advance