dead batteries both coach and chassis

[Sandy]

We recently bought a 2000 Palm Breeze. We have been having problems with a dead battery on the chassis. We have a new battery and the alternator tested great. But it goes dead when parked.

This week we turned off the power at the panel on the steps and thought that would solve the problem.

But now the panel is also dead and nether switch (chassis or coach) will turn on.

First off I need to know which battery powers the power on/off panel is it the coach or the chassis battery?

Second I need to know how I decifer what is causing the chassis battery to go dead.

The only thing we can think of is the backup camera that the previous owner installed. He took the power off one of the rear roof lights. The monitor only works when the headlights are turned on but we wonder about the camera.

Please help...
thanks much,
Sandy