System Outline

1. HEATER BLOWER MOTOR OPERATION
Current is applied at all times through HTR (50A) fuse to TERMINAL 1 of the heater relay. When the ignition SW is turned ON, current flows through HEATER (10A) fuse to TERMINAL 5 of the heater relay --> TERMINAL 3 --> TERMINAL HR of the A/C amplifier. At the same time, current also flows from HEATER (10A) fuse to TERMINAL IG of the A/C amplifier and TERMINAL 4 of the extra high speed relay --> TERMINAL 3 --> TERMINAL FR of the A/C amplifier.

(Low Speed Operation)
When the blower SW (heater control SW) is pushed to LOW SPEED position, the current to TERMINAL HR of the A/C amplifier flows to TERMINAL GND of the A/C amplifier --> GROUND and turns the heater relay ON. As a result, the current to TERMINAL 1 of the heater relay flows to TERMINAL 2 --> TERMINAL 2 of the blower motor --> TERMINAL 1 --> TERMINAL 1 of the A/C power transistor --> TERMINAL 4 --> GROUND and causes the blower motor to rotate at low speed.

(High Speed Operation)
When the blower SW (heater control SW) is pushed to HIGH SPEED position, the current to TERMINAL HR of the A/C amplifier flows to TERMINAL GND of the A/C amplifier --> GROUND and turns the heater relay ON. At the same time, the current to TERMINAL 4 of the extra high speed relay also flows to TERMINAL 3 of the relay --> TERMINAL FR of the A/C amplifier --> TERMINAL GND --> GROUND and turns the extra high speed relay ON. As a result, the current to TERMINAL 1 of the heater relay flows to TERMINAL 2 --> TERMINAL 2 of the blower motor --> TERMINAL 1 --> TERMINAL 1 of the extra high speed relay --> TERMINAL 4 --> GROUND without passing through the blower resistor, causing the blower motor to rotate at high speed.

(Medium Speed Operation)
When the blower SW (heater control SW) is pushed to MED position, the current to TERMINAL HR of the A/C amplifier flows to TERMINAL GND --> GROUND and turns the heater relay ON. Then, the current to TERMINAL IG of the A/C amplifier flows to TERMINAL BLW --> TERMINAL 2 of the A/C power transistor --> TERMINAL 4 --> GROUND.

As a result, the current to TERMINAL 1 of the heater relay flows to TERMINAL 2 --> TERMINAL 2 of the blower motor --> TERMINAL 1 --> TERMINAL 1 of the A/C power transistor --> TERMINAL 4 --> GROUND and the blower motor is rotated at medium speed by the A/C amplifier controlling the current flowing from TERMINAL 2 of the A/C power transistor to TERMINAL 4.

(DEF Synchronized Control Function)
When the DEF SW in the air vent mode control SW (heater control SW) is pushed, a signal is input into TERMINAL S-DEF of the A/C amplifier. This causes the A/C ON and the blower SW is turned to auto mode.

(Auto Function)
When the auto SW in the heater control SW is pushed, a signal is input into TERMINALS S-BAUTO and S-MAUTO of the A/C amplifier. At the same time, the room temp. decided by the air mix control SW (heater control SW) is input into TERMINAL TSET of the A/C amplifier as a signal. The signal of solar sensor is input into TERMINAL TAM of the A/C amplifier and the signal of A/C room temp. sensor is input into TERMINAL TR of the A/C amplifier. As a result, A/C system is activated by the signal of each sensor to get the room temp. decided by the air mix control SW and the A/C system takes the proper measures for it.

2. OPERATION AIR INLET CONTROL SERVO MOTOR
(Switching from fresh to RECIRC)
With ignition SW turned ON, when the RECIRC SW is pushed, the current flows from HEATER (10A) fuse to TERMINAL 2 of the air inlet control servo motor --> TERMINAL 4 --> TERMINAL MREC of the A/C amplifier --> TERMINAL GND --> GROUND. The motor rotates and the damper moves to the RECIRC side. When the damper is moved to the RECIRC position, the circuit is cut inside the servo motor and the damper stops in that position.

(Switching from RECIRC to fresh)
With the ignition SW turned ON, when the fresh SW is pushed, the current flows from TERMINAL 2 of air inlet control servo motor --> TERMINAL 3 --> TERMINAL MFRS of the A/C amplifier --> TERMINAL GND --> GROUND. The motor rotates and the damper stops at that position.

3. OPERATION OF AIR VENT MODE CONTROL SERVO MOTOR
(Switching from DEF to face)
When the air vent mode control SW (heater control SW) is changed from DEF position to FACE position, a signal is input into TERMINAL 4 of the air vent mode control servo motor from TERMINAL FAC of the heater control SW. This causes the servo motor to rotate and the damper to move from DEF position to FACE position.

(Switching from face to DEF)
When the air vent mode control SW (heater control SW) is changed from FACE position to DEF position, a signal is input into TERMINAL S-DEF of the A/C amplifier from TERMINAL SDEF of the heater control SW. As a result, a signal is input from TERMINAL DEF of the A/C amplifier into TERMINAL 8 of the air vent mode control servo motor, causing the servo motor to rotate and the damper to move from FACE position to DEF position.

4. OPERATION OF AIR MIX CONTROL SERVO MOTOR
When the temperature SW (heater control SW) is turned to "cool" side the current flows from TERMINAL AMC of the A/C amplifier --> TERMINAL 1 of the air mix control servo motor --> motor --> TERMINAL 2 --> TERMINAL AMH of the A/C amplifier --> GROUND and the motor rotates. The damper opening angle at this time is input from TERMINAL 3 of the servo motor to TERMINAL TP of the A/C amplifier. This is used to determine the DAMPER STOP position and maintain the set temperature.

When the air mix control servo SW is turned to the hot side, the current flows from TERMINAL AMH of the A/C amplifier --> TERMINAL 2 of the air mix control servo motor --> motor --> TERMINAL 1 --> TERMINAL AMC of the A/C amplifier, rotating the motor in reverse and switching the damper from "cool" to hot side.

5. AIR CONDITIONING OPERATION
The A/C amplifier receives various signals. i.e., the engine RPM from the igniter, outlet temperature signal from the A/C ambient temp. sensor, coolant temperature from the A/C thermistor and the lock signal from the A/C compressor, etc.

When the engine is started and the A/C SW is ON, a signal is input to the A/C amplifier.

As a result, the GROUND circuit in the A/C amplifier is closed and current flows from HEATER (10A) fuse to TERMINAL 1 of the MG CLT relay --> TERMINAL 2 --> TERMINAL MGC of the A/C amplifier --> TERMINAL GND --> GROUND, turning the MG CLT relay ON. So that the 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. Open direction to avoid lowering the engine RPM during A/C operating.

If the A/C amplifier detects the following conditions, it stops the air conditioning.
^ T he temperature at the air vents is low.
^ There is a marked difference between the compressor speed and the engine speed.
^ The refrigerant pressure is abnormally high or abnormally low.
^ The engine speed decreases.
^ Rapid acceleration occurs.