System Outline

1. HEATER BLOWER OPERATION
Manual Blower Operation
When the blower control SW is set to any blower speed, the A/C control assembly operates and the current to drive the blower motor flows from TERMINAL BLW of the A/C control assembly to TERMINAL SI of the blower motor control relay. The current activates the relay and the voltage applied to TERMINAL +B of the blower motor control relay is output at TERMINAL M+ as the voltage for the selected blower speed. The current then flows from TERMINAL M+ of the blower motor control relay to TERMINAL 2 --> TERMINAL 1 --> TERMINAL M- of blower motor control relay --> TERMINAL GND --> GROUND, and the blower motor operates at the blower speed selected.

Auto Function
When the auto SW is turned ON, the A/C control assembly calculates the required vent temperature based on the set temperature and input from each sensor. Then TERMINAL BLW of the A/C control assembly inputs current to TERMINAL SI of the blower motor control relay in conformity with the required vent output. This current activates the blower motor control relay so that current flows from TERMINAL M+ of the blower motor control relay --> TERMINAL 2 of blower motor--> TERMINAL 1 --> TERMINAL M- of Blower motor control relay --> TERMINAL GND --> GROUND, activating the blower motor. The blower motor then operates at different steps in conformity with variable current flow output from TERMINAL BLW of the A/C control assembly to TERMINAL SI of the blower motor control relay.

2. OPERATION OF AIR INLET CONTROL SERVO MOTOR
(Switching From Fresh To Recirc)
With Ignition SW turned ON, the current flows from HTR fuse to TERMINAL IG of A/C control assembly --> TERMINAL MREC -->TERMINAL 6 of air inlet control servo motor --> TERMINAL 2 --> TERMINAL MFRS of A/C control assembly --> TERMINAL GND --> GROUND, the motor rotates and the damper moves to the recirc side. When the damper operates with the A/C SW at RECIRCposition, the DAMPER position signal is input from TERMINAL 5 of the servo motor to TERMINAL TPI of the ECU (built into the A/C control assembly). As a result, current to the servo motor circuit is cut OFF by the ECU, so the damper stops at that position.

(Switching From Recirc To Fresh)
With Ignition SW turned ON, when the recirc/fresh SW is switched to the fresh side, the current flows from TERMINAL IG of A/C control assembly --> TERMINAL MFRS --> TERMINAL 2 of Air inlet control servo motor --> TERMINAL 6 --> TERMINAL MREC of A/C control assembly --> TERMINAL GND --> GROUND, the motor rotates and the damper stops at that position.

3. OPERATION OF AIR VENT MODE CONTROL SERVO MOTOR
With Ignition SW turned ON, the current flows from HTR fuse to TERMINAL IG of A/C control assembly.

(Switching From DEF To Face)
The current flows from TERMINAL MFACE of A/C control assembly --> TERMINAL 4 of air vent control servo motor --> TERMINAL 5 --> TERMINAL MDEF of A/C control assembly --> TERMINAL GND --> GROUND. The motor rotates and the damper moves to the face side. When the damper operates with the A/C SW at face position, the DAMPER position signal is input from TERMINAL 1 of the servo motor to the TERMINAL TPM of the ECU (built into the A/C control assembly). As a result, current to the servo motor circuit is cut OFF by the ECU, so the damper stops at that position.

(Switching From Face To DEF)
The current flows from TERMINAL MDEF of A/C control assembly --> TERMINAL 5 of air vent control servo motor --> TERMINAL 4 --> TERMINAL MFACE of A/C control assembly --> TERMINAL GND --> GROUND, the motor rotates and the damper stops at that position.

4. OPERATION OF AIR MIX CONTROL SERVO MOTOR
When the temperature SW is turned to the "cool" side, the current flows from TERMINAL MC of A/C control assembly --> TERMINAL 4 of air mix control servo motor --> motor --> TERMINAL 5 --> TERMINAL MH of A/C control assembly --> TERMINAL GND --> GROUND and the motor rotates. The damper opening angle at this time is input from TERMINAL 1 of servo motor to TERMINAL TP of A/C control assembly, this is used to determine the DAMPER STOP position and maintain the set temperature.

When the temperature control SW is turned to the "hot" side, the current flows from servo motor --> TERMINAL MH of A/C control assembly --> TERMINAL 5 of air mix control servo motor --> motor --> TERMINAL 4 --> TERMINAL MC of A/C control assembly --> TERMINAL GND --> GROUND, rotating the motor in reverse and switching the damper from cool to hot side.

5. AIR CONDITIONING OPERATION
The A/C control assembly receives various signals, i.e., the engine RPM from the igniter, outlet temperature signal from the A/C thermistor, coolant temperature from the engine coolant temp. Sensor(water temp. sensor) and the lock signal from the A/C compressor, etc.

When the engine is started and the A/C SW (A/C control assembly) is on, a signal is input to the ECU (built in the A/C control assembly). As a result, the ground circuit in A/C control assembly is closed and current flows from HTR fuse to TERMINAL 1 of A/C magnetic clutch relay --> TERMINAL 2 --> TERMINAL ACMG of engine control module --> TERMINAL A/C --> TERMINAL MGC of the A/C control assembly --> TERMINAL GND --> 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 (engine and electronically controlled transmission ECU detects the magnetic clutch is ON and the A/C compressor operates. Open direction to avoid lowering the engine RPM during A/C operating.

When any of the following signals are input to the A/C control assembly, the control assembly operates to turn OFF the air conditioning.

- Engine RPM. Signal is high.
- Coolant high 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.