Heating and Air Conditioning: Description and Operation

1. HEATER BLOWER MOTOR OPERATION
Current is applied at all times through the FL HEATER fuse to TERMINAL 5 of the heater relay. When the ignition SW is turned ON, current flows through the GAUGE fuse to TERMINAL 3 of the heater relay --> TERMINAL 1 --> TERMINAL HR of the A/C automatic amplifier. At the same time, current also flows from the GAUGE fuse to TERMINAL IG of the A/C automatic amplifier and TERMINAL 4 of the slower HI relay --> TERMINAL 3 --> TERMINAL FR of the A/C automatic amplifier and TERMINAL B13 of the blower SW.

(Low Speed Operation)
When the blower SW is pushed to LO position, the current to TERMINAL HR of the A/C automatic amplifier flows to TERMINAL GND of the A/C automatic amplifier --> GROUND and turns 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 motor --> TERMINAL 2 --> TERMINAL 1 of the A/C power transistor --> TERMINAL 2 --> GROUND and causes the blower motor to rotate at low speed.

(High Speed Operation)
When the blower SW is pushed to HI position, the current to TERMINAL HR of the A/C automatic amplifier flows to TERMINAL GND of the A/C automatic amplifier --> GROUND and turns the heater relay ON. At the same time, the current to TERMINAL 4 of the blower HI relay also flows to TERMINAL 3 of the relay TERMINAL FR of the A/C automatic amplifier --> TERMINAL GND --> GROUND and turns the blower HI relay ON. As a result, the current to TERMINAL 5 of the heater relay flows to TERMINAL 4 --> TERMINAL 1 of the blower motor --> TERMINAL 2 --> TERMINAL 1 of the blower HI relay --> TERMINAL 2 --> GROUND without passing through the blower resistor, causing the blower motor to rotate at high speed.

(Medium Speed Operation)
When the blower SW is pushed to M1 or M2 position, the current to TERMINAL HR of the A/C automatic amplifier flows to TERMINAL GND --> GROUND and turns the heater relay ON. Then, the current to TERMINAL IG of the A/C automatic amplifier flows to TERMINAL BLW --> TERMINAL 3 of the A/C power transistor TERMINAL 2 --> GROUND.
As a result, the current to TERMINAL 5 of the heater relay flows to TERMINAL 4 --> TERMINAL 1 of the blower motor --> TERMINAL 2 --> TERMINAL 1 of the A/C power transistor --> TERMINAL 2 --> GROUND and the blower motor is rotated at medium speed by the A/C automatic amplifier controlling the current flowing from TERMINAL 3 of the A/C power transistor to TERMINAL 2.

(DEF Synchronized Control Function)
When the DEF SW in the mode selection SW is pushed, a signal is input into TERMINAL DEF of the A/C automatic 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 TERMINAL BAUTO of the A/C automatic amplifier. At the same time, the room temp. decided by the heater control SW is input into TERMINAL TSET of the A/C automatic amplifier as a signal, a signal of the A/C solar sensor is input into TERMINAL TS of the A/C automatic amplifier and a signal of the A/C room temp. Sensor is input into TERMINAL TR of the A/C automatic amplifier. As a result, A/C system is activated by the signal of each sensor to get the room temp. Decided by the heater control SW and the A/C system takes the proper measures for it.

2. OPERATION OF AIR INLET CONTROL SERVO MOTOR
(Switching From Fresh To Recirc)
With ignition SW turned ON, when the recirc SW is pushed, current flows from the GAUGE fuse to TERMINAL 1 of the air inlet control servo motor --> TERMINAL 3 --> TERMINAL REC of the A/C automatic 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 OFF inside the servo motor and the damper stops at that position.

(Switching From Recirc To Fresh)
With the ignition SW turned ON, when the fresh SW is pushed, current flows from TERMINAL 1 of the air inlet control servo motor --> TERMINAL 2 --> TERMINAL FRS of the A/C automatic amplifier --> TERMINAL GND --> GROUND, the motor rotates and the damper moves to the FRESH side. When the damper is moved to the FRESH position, the circuit is cut off 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, current flows from the 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 B4 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 A 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 'warm' 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 'warm' 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
The A/C automatic 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, etc.
When the engine is started and the A/C SW is ON, a signal is input to the A/C automatic amplifier.
As a result, the ground circuit in the A/C automatic amplifier is closed.
At the same time, the engine control module detects the A/C magnetic clutch is ON and the A/C automatic amplifier operates.
Open direction to avoid lowering the engine RPM during A/C operating.
If the A/C automatic amplifier detects the following conditions, it stops the air conditioning.
- The 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.