For 1990-2009 cars

Air is directed through or around the heater core. The temperature valve inside of the HVAC module assembly moves in order to direct airflow. When all of the air is forced through the heater core, maximum heating is obtained. When all of the air is routed around the heater core, no heat is obtained.

The temperature valve actuator, which mounts onto the HVAC module, operates the temperature valve. The actuator contains a reversible DC motor. The motor responds to a voltage signal from the temperature knob in the heater and A/C control.

With the ignition switch in RUN, battery voltage is supplied to the heater and A/C control temperature knob.

When the temperature control knob is fully to the left (COOL), the following actions occur:

• | Less than 0.1 volt is supplied to the temperature valve actuator.

• | The actuator operates the temperature valve in order to completely block the air flow through the heater core.

• | No heating is obtained.

When the temperature control knob is fully to the right (WARM), the following actions occur:

• | Battery voltage is supplied to the temperature valve actuator.

• | The actuator operates the temperature valve in order to direct all of the air through the heater core.

• | Maximum heating is obtained.