The purpose of the auxiliary heating system is to supply heat to the interior of the ambulance body. The HVAC control panel is located on the front interior wall of the ambulance body and controls HVAC operation. Placing the HVAC switch in the OFF position turns on the solenoid closing the water valve. This action will not allow coolant to flow through the booster pump or auxiliary heater core. The location of the water valve is under the vehicle on the right outer frame rail. When heat is desired the HVAC switch is in the ON position and the valve is opened. Coolant will then flow to the booster pump. The booster pump electrically pumps the coolant though the heater core of the rear HVAC module. The booster pump is located under the vehicle on the right outer frame rail.