System Outline

1. HEATER BLOWER OPERATION
Manual operation
When the blower speed is set to a certain level using the blower control SW, the A/C control assembly sends the signals to the blower control to control the blower motor speed.

Auto operation
When the auto SW is turned ON, the A/C control assembly sends the signals from various sensors and temperature SW to the blower control to automatically control the blower motor speed.

2. AIR INLET CONTROL SERVO MOTOR CONTROL
When the FRESH/RECIRC select SW is set to RECIRC, the motor in the air inlet control servo motor starts rotating to move the damper toward the RECIRC side. Since the damper position is detected by the TERMINAL TP1 of the A/C control assembly, the motor is continuously rotated until the damper reaches its stop position.When the FRESH/RECIRC select SW is set to FRESH, the motor in the air inlet control servo motor starts rotating to move the damper toward the FRESH side. Since the damper position is detected by the TERMINAL TPI of the A/C control assembly, the motor is continuously rotated until the damper reaches its stop position.When the FRESH/RECIRC select SW is set to AUTO, the exhaust gas sensor installed in the engine room monitors contents in the exhaust gas and FRESH or RECIRC is automatically switched.

3. AIR VENT MODE CONTROL SERVO MOTOR CONTROL
When the mode select SW is pushed, the ECU in the A/C control assembly activates the air vent mode control servo motor. This causes the servo motor to rotate to the position (FACE, BI-LEVEL, FOOT, FOOT/DEF, DEF) selected using the mode select SW, and moves the film damper.

4. AIR MIX CONTROL SERVO MOTOR CONTROL
When the temperature control SW on the driver's side is pressed, the ECU in the A/C control assembly sends a signal to the air mix control servo motor on the driver's side. This signal drives the motor to reach the temperature set by the temperature control SW on the driver's side, and moves the film damper. Passenger's side is operated as same as the driver's side.

5. AIR CONDITIONING OPERATION
The A/C control assembly receives various signals, I.E., the engine RPM from the crankshaft position sensor, outlet temperature signal from the A/C ambient temp. sensor, coolant temperature from the engine coolant temp. sensor and the lock signal from the NC compressor, etc. When the engine is started and the A/C SW is on, o signal is input to the ECU (Built into the A/C control assembly). As a result, the ground circuit in A/C control assembly is closed and current flows front HTR fuse to TERMINAL 1 of the A/C COMP relay to TERMINAL 2 to TERMINAL ACMG of file engine control module to TERMINAL MPX2 to TERMINAL MPX+ of the A/C control assembly to TERMINAL GND to GROUND, turning the relay on so that the A/C magnetic clutch is ON and the A/C compressor operates. At the same time, the engine control module detects the magnetic clutch is on and the A/C compressor operates and rotates the motor to the open direction to avoid lowering the engine RPM during A/C operation. When any of the following signals are input to the A/C control assembly, the control assembly operates to turn OFF the air conditioning.
* Coolant temp. signal is high.
* A signal that the temperature at the air outlet is low.
* A signal that there is a large difference between engine speed and compressor speed.
* A signal that the refrigerant pressure is abnormally high or low.