I have a couple of questions for you, first is the solar system you refer to the 10 watt that Winnebago was installing on a lot of coaches. second is do you have the electrical schematics for your rig?
If the answer to the first is yes, I don't think that the solar system is at fault. Don't worry about it.
If the answer to the second is yes, you should look at the battery switches how they are operating, I would bet the converter is supplying powere to one of the switches and that switch is bad. By switch, I mean solenoid, not toggle or other manually operated switch. I would start there looking for trouble. If the answer is no, download it from Winnebagoind.com. You'll find it under the resources tab.
The circuits are right there and should be easy to trouble shoot.
I have a third question, does your rig charge both batteries and the 12 volt system work when the engine is running and you are disconnected from shore power?
