1.Air mix servomotor
(1)Construction
The air mix servomotor consists of the motor, limiter, potentiometer and moving contact, etc., as shown in the figure and it is activated by the signal from the ECU.
(2)Operation
When the air mix damper is shifted to HOT, the MH terminal will be the power source and the MC terminal will be the ground to rotate the servomotor to make the shift. When the MC terminal becomes the power source and the MH terminal becomes the ground, the servomotor rotates in the opposite direction to shift the air mix damper to COOL.
The moving contact of the potentiometer moves in synchronicity with the servomotor revolving, generates electric signals according to the damper position, and feeds back the actual damper position to the ECU. When the damper comes to the desired position, the air mix servomotor stops the current to the servomotor.
The air mix servomotor is equipped with a limiter that shuts off the current to the motor when full-stroke movement is activated. When the moving contact that synchronizes with the servomotor revolving reaches the full-stroke positions, the circuit is open to stop the motor.
2.Air inlet servomotor
(1)Construction
The air inlet servomotor consists of the motor, gear, moving plate, etc., as shown in the figure.
(2)Operation
Pressing the air inlet control switch will generate the ground circuit for the servomotor to allow the current to the motor and moves the air inlet damper.
When the damper is changed to FRESH or RECIRC position, the contact of the moving plate linked with the motor is released and the circuit is open to stop the motor.
3.Airflow servomotor
(1)Construction
The airflow servomotor consists of the motor, moving contact, circuit plate, motor drive circuit, etc., as shown in the figure.
(2)Operation
When the airflow control switch is operated, the motor drive circuit determines whether the damper position changes to the right or left side and directs the flow of current to the motor to shift the moving contact linked to the motor.
When the moving contact moves to the position according to the airflow control switch position, the contact with the circuit plate is released, the circuit is open and the motor stops.
When the airflow control switch is moved from FACE to DEF
Input A will be 1 because the circuit is open, and input B will be 0 because the grounded circuit is generated. As a result, output D will be 1 and output C will be 0 and allow the current for the motor from D to C. After the motor revolves and moving contact B releases contact with DEF, input B will be 1 because the circuit will be opened. As a result, both output C and D will be 0, the current to the motor is cut and the motor stops.
Some models do not have a contact in the servomotor.
A/C control ECU rotates the motor based on the operation of the selector on the control panel.
Damper position is monitored in reference to the potentiometer voltage that varies according to the motor.