Lloyd,

On my 99 Country Coach, the Central Heat Control is for the bay heaters and there is a separate thermostat in the plumbing bay behind a removable panel. This controls the bay heat for winter use.

The Interior Heat Exchangers controls the coach heat. On my bus there are individual Heat Exchanger panel buttons in the front above the pass. side, one in the galley and another in the bedroom. If you push these switches in, they change color and give a different fan speed. These are two speed fan motors.

The temp is controlled by the thermostat setting when on the Furnace mode.

Thermostat must be on Furnace mode and the Interior Heat Exchanger and Central Heat Control buttons above the driver's seat on for Webasto to work to give heat up and down.

Denny