Heating and Air Conditioning: Description and Operation

Radiator Fan and Air Conditioning

SYSTEM OUTLINE

1. HEATER BLOWER MOTOR OPERATION
The current is applied at all times through the FL ALT fuse to the HTR fuse to TERMINAL 1 of the HTR relay.

When the ignition SW is turned on, the current flows through the GAUGE fuse to TERMINAL 5 of the HTR relay to coil to TERMINAL 3 to TERMINAL 3 of the blower SW.

- Low speed operation
When the blower SW is moved to LO position, the current flows to TERMINAL 3 of the blower SW to TERMINAL 1 to GROUND, turning the HTR relay on. This causes the current to flow from the HTR fuse to TERMINAL 1 of the HTR relay to TERMINAL 2 to TERMINAL 1 of the blower motor to TERMINAL 2 to TERMINAL 4 of the blower resistor to TERMINAL 1 to GROUND, rotating the blower motor at low speed.

- Medium speed operation (Operation at M1, M2)
When the blower SW is moved to M1 position, the current flows to TERMINAL 3 of the blower SW to TERMINAL 1 to GROUND, turning the HTR relay on. This causes the current to flow from the HTR fuse to TERMINAL 1 of the HTR relay to TERMINAL 2 to TERMINAL 1 of the blower motor to TERMINAL 2 to TERMINAL 4 of the blower resistor to TERMINAL 3 to TERMINAL 4 of the blower SW to TERMINAL 1 to GROUND. At 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, the current through the motor flows from TERMINAL 4 of the blower resistor to TERMINAL 2 to TERMINAL 8 of the blower SW to TERMINAL 1 to GROUND. At 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 3 of the blower SW to TERMINAL 1 to GROUND, turning the HTR relay on.

This causes the current to flow from the HTR fuse to TERMINAL 1 of the HTR relay to TERMINAL 2 to TERMINAL 1 of the blower motor to TERMINAL 2 to TERMINAL 5 of the blower SW to TERMINAL 1 to GROUND, rotating the blower motor at high speed.

2. FAN MOTOR OPERATION
When the ignition SW is turned on, the current from the ECU-IG fuse flows to the FAN NO.1 relay (Coil side) and the A.C FAN NO.2 relay (Coil side) to TERMINAL 3 of the A/C single pressure SW to TERMINAL 2 to engine control module. Electric current passed to engine control module receives the signal from engine coolant temperature sensor and is sent from engine control module to GROUND, and the FAN NO.1 relay is turned off and the A.C FAN NO.2 relay is turned on.

At the same time as this current flow, the current from the ECU-IG fuse flows to the ENGINE MAIN relay (Coil side) to GROUND, turning the ENGINE MAIN relay on. As a result, current from the FL ALT fuse flows to the CDS fuse and RDI fuse.

- Low speed operation
When the ignition SW is turned on and the A/C is activated, the current flows from the FL ALT fuse to the HTR fuse to the HTR relay (Point side) to the A.C fuse to the A.C MG relay (Point side) to the A.C FAN NO.3 relay (Coil side) to GROUND, turning the A.C FAN NO.3 relay on. As a result, the current from the CDS fuse flows to TERMINAL 2 of the A/C condenser fan motor to TERMINAL 1 to the A.C FAN NO.2 relay (Point side) to the A.C FAN NO.3 relay (Point side) to TERMINAL 2 of the radiator fan motor to TERMINAL 1 to GROUND. As a result, the fans are activated at low speed. If the engine coolant temperature is approx. 90 °C (194 °F) or less, and the refrigerant pressure is approx. 15.5 kg/sq.cm (220 psi, 1520 kPa) or less, both the water temperature SW (Radiator fan) and the A/C single pressure SW are closed, so the FAN NO.1 relay is turned off and the A.C FAN NO.2 relay is turned on. As a result, each fan motor operates at low speed.

- High speed operation
During A/C operation, if the refrigerant pressure becomes higher than ordinary level (Approx. 15.5 kgflcm2 (220 psi, 1520 kPa)), the A/C single pressure SW is turned off. As a result, the FAN NO.1 relay is turned on and the A.C FAN NO.2 relay is turned off, and the current flows from the RDI fuse to FAN NO.1 relay (Point side) to TERMINAL 2 of the radiator fan motor to TERMINAL 1 to GROUND, and the current from the CDS fuse flows to TERMINAL 2 of the A/C condenser fan motor to TERMINAL 1 to A.C FAN NO.2 relay (Point side) to GROUND, reaching each fan motor in parallel, thus causing the fan motors to operate at high speed.

Note that, because the current flows in the same manner even if the engine coolant temperature is approx. 90 °C (194 °F) or higher, the fan motors still operate at high speed.

3. AIR INLET CONTROL SERVO MOTOR OPERATION
- Switching from FRESH to RECIRC
With the ignition SW turned on, current flows from the GAUGE fuse to TERMINAL 5 of the air inlet control servo motor. When the RECIRC/FRESH SW is switched to the RECIRC side, current flows from TERMINAL 5 of the air inlet control servo motor to TERMINAL 1 to TERMINAL 3 of the heater control SW to TERMINAL 8 to GROUND. The motor rotates and the damper moves to the RECIRC side. When it is in the RECIRC position, current is cut inside the servo motor and the damper stops at that position.

- Switching from RECIRC to FRESH
With the ignition SW turned on, when the RECIRC/FRESH SW is switched to the FRESH side, current flows from TERMINAL 5 of the air inlet control servo motor to TERMINAL 2 to TERMINAL 4 of the heater control SW to TERMINAL 8 to GROUND, the motor rotates and the damper moves to the FRESH side. When it is in the FRESH position, current is cut inside the servo motor and the damper stops at that position.

4. AIR CONDITIONING OPERATION
When the blower SW is set on, the current from the FL ALT fuse flows to the HTR fuse to the HTR relay (Point side) to the A.C fuse to TERMINAL 1 of the A/C dual pressure SW to TERMINAL 4 to TERMINAL 2 of the A/C amplifier. The engine RPM signal from the engine control module, the evaporator temperature signal from the A/C evaporator temperature sensor and the lock signal from the lock sensor 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 the TERMINAL 7 of the A/C amplifier. At the same time, the current flows from the A.C fuse to TERMINAL 1 of the A.C MG relay to coil to TERMINAL 2 to TERMINAL 11 of the A/C amplifier to TERMINAL 5 to GROUND, turning the A.C MG relay on.

This causes the current from the A.C fuse to flow to the A/C magnetic clutch, turning the A/C magnetic clutch on. When any of the following signals are input to the A/C amplifier, the amplifier operates to turn off the air conditioning.

- Engine low RPM signal.

- A signal that the temperature at evaporator is low.

- A signal that the refrigerant pressure is abnormally high or low.

- A signal that the A/C compressor is locked.

5. DEF SYNCHRONIZED CONTROL FUNCTION
When the air vent mode control lever is turned to DEF mode, the A/C SW is automatically turned on.