What does the switch in the monitor panel do?

[skater]

It's the switch for the water pump, which is used when you are not using city water - you'd fill the tank, then turn that switch on to pressurize the system and provide water when you need it.

When you flip the switch on, the pump should run for a moment to build pressure in the system (and don't worry - if it's working you should hear it), then shut off and stay off until you open a faucet. The pump is controlled by pressure - when the water pressure drops below a certain set amount, it kicks on, then when it exceeds a certain (higher) pressure, it shuts off.

A useful quirk of this system is that it's easy to test for leaks in the water system: let it build up pressure then do...nothing. If it turns on again, you have a leak somewhere. (Mine will sit for several hours before it needs to run again, so there might be a tiny leak somewhere, but I'm not going to worry about it - but if it's kicking on a couple times an hour or more, definitely start looking.)

In my '91 the pump is mounted inside the right rear door - there's a small access panel there and you can see the pump just inside.