Heating and Air Conditioning: Description and Operation

1. HEATER BLOWER MOTOR OPERATION
Current is applied at all times through the HEATER fuse to TERMINAL 5 of heater relay.

When the ignition SW is turned ON, current flows through ECU-IG fuse to TERMINAL 3 of the heater relay --> coil --> TERMINAL 1 --> TERMINAL 5 of the blower SW.

* Low speed operation
When the blower SW is moved to LO position, the current flows to TERMINAL 1 of blower SW --> TERMINAL 8 --> GROUND, causing the heater relay to ON. This causes the current flowing from the HEATER fuse to TERMINAL 5 of the heater relay --> TERMINAL 4 --> TERMINAL 1 of the blower motor --> TERMINAL 2 --> TERMINAL 1 of the blower resistor --> TERMINAL 4 --> GROUND, causing the blower motor to rotate at low speed.

* Medium Speed Operation (Operation at M1, M2)
When the blower SW is moved to M1 position, the current flowing to TERMINAL 1 of blower SW --> TERMINAL 8 --> GROUND, and turned the heater relay ON. This causes the current flowing from the heater fuse to TERMINAL 5 of the heater relay --> TERMINAL 4 --> TERMINAL 1 the blower motor --> TERMINAL 2 --> TERMINAL 1 of the blower resistor --> TERMINAL 2 --> TERMINAL 3 of the blower SW --> TERMINAL 8 --> GROUND. This time, the blower resistance of the blower resistor is less than at low speed, so the blower motor rotates at medium low speed.

When the blower SW is moved to M2 position, current flowing through the motor flows from TERMINAL 1 of the blower resistor --> TERMINAL 3 --> TERMINAL 2 of the blower SW --> TERMINAL 8 --> GROUND. This time, resistance of the blower resistor is less than at M1 position, so the blower motor rotates at medium high speed.

* High Speed Operation
When the blower SW is moved to HI position, the current flows to TERMINAL 1 of blower SW --> TERMINAL 8 --> GROUND and turns the heater relay ON.

This causes the current flowing from the heater fuse to TERMINAL 5 of the heater relay --> TERMINAL 4 --> TERMINAL 1 of blower motor --> TERMINAL 2 --> TERMINAL 6 of blower SW --> TERMINAL 8 --> GROUND, causing the blower motor to rotate at high speed.

2. RADIATOR FAN AND CONDENSER FAN OPERATION
When the ignition SW is turned ON, the current flows from the ECU-IG fuse to TERMINAL 2 of the fan relay --> TERMINAL 1 --> TERMINAL 3 of the A/C single pressure SW --> TERMINAL 2 --> TERMINAL 1 of the engine coolant temp. SW --> GROUND, activating the relay. At this time, current is supplied from RAD FAN fuse to TERMINAL 4 of the relay. At the same time, current from the ECU-IG fuse through TERMINAL 1 of the A.C fan No.2 relay --> coil --> TERMINAL 2 --> A/C single pressure SW --> engine coolant temp. SW --> GROUND, then through the CDS FAN fuse --> TERMINAL 2 of the A/C condenser fan motor --> TERMINAL 1 --> TERMINAL 3 of the No.2 relay --> TERMINAL 5 --> TERMINAL 3 of the A.C fan No.3 relay.

* Low Speed Operation
When the A/C magnetic clutch is turned ON during A/C operation, current from the A/C fuse flows through TERMINAL 2 of the A/C magnetic clutch relay --> TERMINAL 4 --> TERMINAL 1 of the A.C fan No.3 relay --> TERMINAL 2 --> GROUND, activating No.3 relay. Then the current applied to TERMINAL 3 of relay No.3 flows through TERMINAL 5 --> TERMINAL 2 of the radiator fan motor --> TERMINAL 1 --> GROUND. Since the condenser and radiator fan motors are connected in series, both fans rotate at low speed.

* High Speed Operation
During A/C operation when the water temp. reaches approx. 90° C (194° F) or more (engine coolant temp. SW is off) or the refrigerant pressure reaches 1373 kPa (14 Kg/cm2, 199 psi) or more (A/C single pressure SW is OFF), current to the fan relay and A/C fan No.2 relay is OFF and that to the motor is supplied in parallel, causing the motor to rotate at high speed.

3. AIR CONDITIONING OPERATION
When the blower SW is set ON, current from the A/C fuse flows through TERMINAL 1 of the A/C dual pressure SW --> TERMINAL 4 --> TERMINAL A-1 or B-2 of the A/C amplifier the engine rpm signal from ignition, the evaporator temp. signal from the A/C thermistor and the lock signal from the A/C compressor (W/ power steering) are all supplied to the A/C amplifier.

When the A/C SW is turned ON, the A/C SW ON signal is sent to activate the A/C amplifier. Current flows from the A/C fuse --> TERMINAL 1 of the magnetic clutch relay --> coil --> TERMINAL 3 --> TERMINAL A-9 or B-11 of amplifier --> TERMINAL A-4 or B-5 --> GROUND, turning the magnetic clutch relay ON.

This causes current from the A/C fuse to flow to the magnetic clutch, turning the compressor ON.
When any of the following signals are input to the A/C amplifier, the amplifier operates to turn off the air conditioning.
* Engine high RPM signal.
* A signal that the temperature at evaporate is low.
* A signal that the refrigerant pressure is abnormally High or Low.
* A signal that the temperature at A/C compressor is high.