The wiring diagram for your camper is posted on the site's tech drawings. It appears you have a break in the connection from the auxiliary battery and/or possibly a bad or miswired battery cut-off relay. The recharge timer is supposed to only feed the auxilliary battery. But the feed also goes to the main via the relay. If the relay is bad or been tampered with, recharge could be feeding the main as well. The relay is a metal-case, mounted on the left side of the engine compartment. This is found when some owners want to recharge the main battery off AC but don't understand the wiring. When this happens, the timer will connect both. I would guess you are currently running DC fridge off of the main because they have been cross-connected. Your aux. is either dead or has blown its fuse. Note: There are internal and in-line fuses NOT shown in the Bentley but are in the Repair Manual Type 2 diagram that is attached. Go to the wiring diagram and trace everything and restore to ORIGINAL. In OE form, the fridge, battery & recharge all work excellent. There are superior ways to recharge the main of DC instead of butchering the OE wiring.