A heating and air-conditioning system has an auxiliary engine for heating and cooling of a vehicle while the primary engine of the vehicle is not operating. The vehicle has a sleeper compartment with a sleeper compartment air conditioning unit powered by the main engine. An auxiliary air conditioning system located exterior of the sleeper compartment is powered by the auxiliary engine. An auxiliary supply duct extends into the sleeper compartment and joins the duct of the sleeper compartment air conditioning unit. A valve operated by air pressure blocks air flow from the sleeper compartment air conditioning unit into the auxiliary duct while in the main position. In the auxiliary position, the valve blocks air flow from the auxiliary duct into the sleeper compartment air conditioning unit.