Control System Outputs - Electronic Automatic Temperature Control (EATC)

Blower Motor Speed Control 

The blower motor speed control is located on the A/C evaporator housing, in the engine compartment.

• The function of the blower motor speed control is to convert low power signals from the heating ventilation air conditioning (HVAC) module to a high current, variable ground feed for the blower motor.
• Blower motor speed is infinitely variable and is controlled by the HVAC module software.
• A delay function provides a gradual increase or decrease in blower motor speed under all conditions.

Temperature Blend Door Actuator  

The temperature blend door actuator is located on the top of the plenum housing.

• Its function is to move the air temperature blend door on command from the control assembly.
• The temperature blend door actuator contains a reversible electric motor and a potentiometer. The potentiometer wiper is connected to the actuator output shaft and moves with the output shaft to indicate the position of the air temperature blend door.
• A 5-volt signal is applied to the ends of the potentiometer. The voltage available at the wiper indicates the position of the potentiometer. The expressed value of the actuator wiper voltage is sent to the HVAC module and is matched with the wiper voltage of the module potentiometer. The control module then drives the actuator motor in the direction necessary to make the actuator wiper voltage agree with the control module wiper voltage.

Vacuum Control Motors 

Vacuum control motors are used to move the floor/panel, panel/defrost and air inlet mode doors.