I have to admit I have never understood fully how the engine charges first the chassis battery and then the house batteries, but it does and on my current rig, there is a solenoid and auto reset CB involved. But then again I have a very entry level rig and it doesn't those momentary switches above the door.
From what little I have learned about the circuit, it sounds like that there may be a problem with the converter. Consistent and cyclic on/off sounds like a build up and discharge of an electronic component rather than an electrical component.
I would do as Chum lee suggests and start at the beginning. As there is an auto reset CB, in the Aux power circuit, I would check that. Sometimes these problems need two people while analyzing things. Someone inside to stop and start the engine as needed and someone to use the DMM. In your case maybe not but remember two heads...
I'm going to the Pomona show today but tomorrow I'll go to the RV and pick up my wiring diagrams from Fleetwood. May give more info, may not.
