Rodger: I think you will find that there is a single 120volt outlet in a weatherproof box in the battery compartment just under the aircleaner and above the webasto, maybe a little forward of the Webasto. The block heater is plugged in there, with the cord extending out through an opening in the cover. At least that's the way my 1990 CC is set up. Power to that outlet is controlled by the switch marked Block Heat on the overhead panel to the left of the driver seat. As noted, it only has power when you are plugged in or gen is running and that switch is on. I like this setup for just the type of use you want. I often use this outlet for patio lights, which are then easily controlled from the dash and don't go through the inverter. Plus, if there was ever a reason to do so, you could plug in the block heater without plugging in the bus. At least where I am located, I seldom use the block heater anyway. It is either plenty warm or we are up skiing and running the webasto for heat, so don't need it. Even for a cold start at home, the Webasto will warm the engine much faster than the block heater. I think the only time I ever used it was once when the Webasto conked out during a ski trip.

Do you throw the chassis battery disconnects when you are parked? I do if parking for over a week. I have not had any problem with my start batteries getting discharged. Maybe that would solve your problem.

Good luck.