[77newell]

On my 93 coach that micros witch controls the boost pump noted in the previous post. However, whether it works or not will only determine the max amount of heat you can get up front. With the fans running if there is no heat at all, then you have at least one valve in the coolant flow circuit to the heater closed. The only valves I know of are the shutoff valves at the engine and the modulating valve up front controlled by the dash heat lever on the dashboard.