Air mix valve and actuator description:
System air is heated, as necessary, by passing it through the heater core. An air mix valve, located inside the heater and A/C module assembly, determines how much air passes around the heater core and how much is forced through the core. When all air is forced through the heater core, maximum heating is obtained. When all air is routed around the heater core, no heating is obtained.
The air mix valve is operated by the air mix valve actuator, which mounts on the heater and A/C module assembly. The actuator contains a reversible DC motor that is powered by the HVAC programmer. The programmer uses information from the heater and A/C control assembly and its network of sensors to determine appropriate air mix valve position. The programmer then powers the actuator motor to run in the direction necessary to move the air mix valve to that position.