The evaporator bay has changed over the years so the valve location and type is going to vary. It is a solenoid valve on the cooling system line going to the heat exchanger in the OTR evaporator compartment. The heat exchanger and the evaporator coil are sandwiched together and the only time coolant should flow through the valve is when you require heat in the coach, or when you need to temper the cooling air of the AC system. If you don't have OTR none of this applies.