Heating and Air Conditioning: Description and Operation

1. HEATER BLOWER MOTOR OPERATION
The current flows constantly from the FL HEATER fuse to TERMINAL 5 of the Heater Relay. When the ignition SW is turned ON, the current flows through GAUGE fuse to TERMINAL 5 of the blower speed control relay, and to TERMINAL 3 of the heater relay TERMINAL 1 --> TERMINAL A-1 of the heater control SW.

* Low Speed Operation
When the blower SW (heater control SW is set to LO position, the current to TERMINAL A-1 of the heater control SW flows to TERMINAL B-16 --> GROUND, activating the heater relay ON. As a result, the current to TERMINAL 5 of the heater relay flows to TERMINAL 4 --> TERMINAL 1 of the blower motors --> TERMINAL 2 --> TERMINAL 1 of the blower resistor --> TERMINAL 4 --> GROUND, causing the blower motors to operate at low speed.

* High Speed Operation
When the blower SW (heater control SW) is set to HI position, the current to TERMINAL A-1 of the heater control SW flows to TERMINAL B-16 --> GROUND, activating the heater relay. As a result, the current to TERMINAL 5 of the blower speed control relay flows to TERMINAL 7 --> TERMINAL B-13 of the heater control SW --> TERMINAL B-16 --> GROUND, activating the blower speed control relay. This causes the current to flow from TERMINAL 5 of the heater relay to TERMINAL 4 --> TERMINAL 1 of the blower motors --> TERMINAL 2 --> TERMINAL 4 of the blower speed control relay --> TERMINAL 3 --> GROUND, causing the blower motors to operate at high speed.

* Medium Speed Operation (operation at M1, M2)
When the blower SW (heater control SW is set to MI position, the current to TERMINAL A-1 of the heater control SW flows to TERMINAL B-16 --> GROUND, activating the heater relay. As a result, the current from TERMINAL 5 of the blower speed control relay to TERMINAL 6 --> TERMINAL B-9 of the heater control SW --> TERMINAL B-16 --> GROUND, activating the blower speed control relay. This causes the current from TERMINAL 5 of the heater relay to TERMINAL 4 --> TERMINAL 1 of the blower motors --> TERMINAL 2 --> TERMINAL 1 of the blower resistor --> TERMINAL 2 --> TERMINAL 1 of the blower speed control relay --> TERMINAL 3 --> GROUND, causing the blower motors to operate at medium low speed. When the blower SW (heater control SW) is set to M2 position, the current to TERMINAL A-1 of the heater control SW flows to TERMINAL B-16 --> GROUND, activating the heater relay. As a result, the current flows from TERMINAL 5 of the blower speed control relay to TERMINAL 8 --> TERMINAL B-10 of the heater control SW --> TERMINAL B-16 --> GROUND, activating the blower speed control relay. This causes the current to flow from TERMINAL 5 of the heater relay to TERMINAL 4 --> TERMINAL 1 of the blower motors --> TERMINAL 2 --> TERMINAL 1 of the blower resistor --> TERMINAL 3 --> TERMINAL 2 of the blower speed control relay --> TERMINAL 3 --> GROUND, causing the blower motor to operate at medium HI speed. The current to the blower motors at this time is stronger than it was for the M1 position, so the blower motors operates faster for M2 than it does for M1.

2. OPERATION AIR INLET CONTROL SERVO MOTOR
(Switching from fresh to RECIRC)
With the Ignition SW turned ON, the current flows from GAUGE fuse to TERMINAL 1 of the air inlet control servo motor. When the RECIRC/fresh SW is switched to the fresh side, the current flows from TERMINAL 1 of the air inlet control servo motor to TERMINAL 3 --> TERMINAL A-18 of the heater control SW --> TERMINAL B-16 --> GROUND, this causes the motor to rotate and the damper to move to the RECIRC side. When it is in the RECIRC position, the current is cut inside the servo motor, and the damper stops at that position.

(Switching from RECIRC to fresh)
With the ignition SW ON, when the RECIRC/Fresh SW is switched to the RECIRC side, the current flows from TERMINAL 1 of the air inlet control servo motor to TERMINAL 2 --> TERMINAL A-19 of the heater control SW --> TERMINAL B-16 --> GROUND, this causes the motor to rotate and damper to move to the fresh side. When it is in the FRESH position, the current is cut inside the servo motor, and the damper stops at that position.

3. OPERATION OF AIR VENT MODE CONTROL SERVO MOTOR
With the ignition SW turned ON, the current flows from GAUGE fuse to TERMINAL 5 of the air vent mode control servo motor --> TERMINAL 6 --> GROUND, and the damper moves to the position of the mode selection SW on the control SW which is ON. When the foot SW of the heater control SW is turned ON with the DEF position, a signal is input from TERMINAL 7 of the air vent mode control servo motor to TERMINAL B-4 of the heater control SW. As a result, the servo motor operates until the damper reaches to DEF position. When this occurs, the signal to the heater control SW is shut OFF and rotation of the motor stops. Switching to other movement is controlled by the servo motor according to the following signals:
1. FACE position, a signal input from TERMINAL 1 of the servo motor to TERMINAL B-14 of the heater control SW.
2. BI-LEVEL position, a signal input from TERMINAL 2 of the servo motor to TERMINAL A-12 of the heater control SW.
3. FOOT position, a signal input from TERMINAL 3 of the servo motor to TERMINAL A-7 of the heater control SW.
4. FOOT/DEF position, a signal input from TERMINAL 4 of the servo motor to TERMINAL B-11 of the heater control SW.

4. AIR MIX CONTROL SERVO MOTOR
Voltage is applied to TERMINALS 11 and 12 of the A/C system amplifier from the temperature control lever inside the heater control SW and from the potentiometer inside the air mix control servo motor. This voltage is kept at a fixed level by the A/C system amplifier. When the temperature control lever of the heater control SW is moved to 'Cool', the voltage applied to TERMINAL 12 of the A/C system amplifier from TERMINAL B-3 of the heater control SW changes. At this time, the A/C system amplifier compares the voltage from TERMINAL 2 of the air mix control servo motor with the voltage applied to TERMINAL 11 of the A/C system amplifier. This activates the A/C system amplifier, so the current flows from TERMINAL 6 of the amplifier to TERMINAL 5 of the air mix control servo motor --> TERMINAL 4 --> TERMINAL 1 of the A/C system amplifier, and the air mix control servo motor changes to the 'Cool' side. Then when the voltage from the potentiometer inside the servo motor equals, the voltage from the temperature control lever inside the heater control SW, the A/C system amplifier cuts OFF power to the motor. When the temperature control lever is moved to the 'Hot' side, the A/C system amplifier operates the same as for 'Cool' operation, so the current flows from TERMINAL 1 of the A/C system amplifier to TERMINAL 4 of the air mix control servo motor --> TERMINAL 5 --> TERMINAL 6 of the A/C system amplifier, changing the motor to the 'Hot' side. When the voltage of the potentiometer and the voltage of the temperature control level are the same, power to the motor is cut OFF.

5. AIR CONDITIONING OPERATION
When the ignition SW is turned ON, the current from the GAUGE fuse flows through the A/C pressure SW to TERMINAL 3 of the A/C amplifier. If the heater control SW is then turned ON, the current flows from the FL HEATER fuse through the A/C fuse to TERMINAL B-17 of the heater control SW. When the A/C is turned ON, the current flows from TERMINAL B-17 of the heater control SW to TERMINAL B-6 --> TERMINAL 2 of the A/C amplifier, activating the A/C amplifier. The current then flows from TERMINAL 7 of the A/C amplifier to TERMINAL 4 of the engine coolant temp. relay --> TERMINAL 3 --> TERMINAL 1 of A/C magnetic clutch --> GROUND. This causes the compressor to start. When the engine coolant temperature is approx. 108° C (226° F), the water temp. SW (A/C) turned ON and the A/C cut relay is activated. This turns the compressor OFF and stops the air conditioning. The air conditioning also turns OFF, if a signal is input to the A/C amplifier that the air outlet temperature is low (below approx. 3° C) or the refrigerant pressure is abnormally low.