Heating and Air Conditioning: Description and Operation

1. HEATER BLOWER MOTOR OPERATION
Current is applied at all times through HTR fuse to TERMINAL 1 of the HTR relay. When the ignition SW is turned ON, current flows through the HEATER fuse to TERMINAL 5 of the HTR relay --> TERMINAL 3 --> TERMINAL HR of the A/C control assembly. At the same time, current also flows from HEATER fuse to TERMINAL IG+ of the A/C control assembly.

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

* High Speed Operation
When the blower SW (A/C control assembly) is pushed to HIGH SPEED position, the current to TERMINAL HR of the A/C control assembly flows to TERMINAL GND of the A/C control assembly --> GROUND and turns the HTR relay ON. As a result, the current to TERMINAL 1 of the HTR relay flows to TERMINAL 2 --> TERMINAL 2 of the blower motor --> TERMINAL 1 --> TERMINAL 4 of the A/C blower motor linear controller --> TERMINAL 2 --> TERMINAL BLW of the A/C control assembly (which is activated when the blower SW is pushed to high speed position) --> TERMINAL GND --> GROUND without passing through the blower resistor, causing the blower motor to rotate at high speed.

2. AIR INLET CONTROL SERVO MOTOR OPERATION
(Switching from fresh to recirc)
With the ignition SW turned ON, the current flows from HEATER fuse to TERMINAL IG+ of the A/C control assembly --> TERMINAL AIR --> TERMINAL 7 of the air inlet control servo motor --> TERMINAL 6 --> TERMINAL AIF of the A/C control assembly --> TERMINAL GND --> GROUND, the motor rotates and the damper moves to the recirc side. When the damper operates with the A/C SW at RECIRC position, the damper position signal is input from TERMINAL 5 of the servo motor to TERMINAL TPI of the ECU (built into the A/C control assembly). As a result, current to the servo motor circuit is cut OFF by the ECU, so 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, the current flows from TERMINAL IG+ of the A/C control assembly --> TERMINAL AIF --> TERMINAL 6 of the air inlet control servo motor --> TERMINAL 7 --> TERMINAL AIR of the A/C control assembly --> TERMINAL GND --> GROUND, the motor rotates and the damper stops at that position.

3. AIR VENT MODE CONTROL SERVO MOTOR OPERATION
When the ignition SW turned ON, the current flows from HEATER fuse to TERMINAL IG+ of the A/C control assembly.

(Switching from DEF to FACE)
The current flows from TERMINAL FACE of the A/C control assembly --> TERMINAL 4 of the air vent mode control servo motor --> TERMINAL 8 --> TERMINAL DEF of the A/C control assembly --> TERMINAL GND --> GROUND. The motor rotates and the damper moves to the face side. When the damper operates with the A/C SW at FACE position, the damper position signal is input from TERMINAL 8 of the servo motor to the TERMINAL DEF of the ECU (built into the A/C control assembly). As a result, current to the servo motor circuit is cut OFF by the ECU, so the damper stops at that position.

(Switching from FACE to DEF)
The current flows from TERMINAL DEF of the A/C control assembly --> TERMINAL 8 of the air vent control servo motor --> TERMINAL 4 --> TERMINAL FACE of the A/C control assembly TERMINAL GND --> GROUND, the motor rotates and the damper stops at that position.

4. AIR MIX CONTROL SERVO MOTOR OPERATION
When the temperature control SW (A/C control assembly) is turned to the "COOL" side the current flows from TERMINAL AMC of the A/C control assembly --> TERMINAL 1 of the air mix control servo motor --> motor --> TERMINAL 2 --> TERMINAL AMH of the A/C control assembly --> 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 control assembly. This is used to determine the damper stop position and maintain the set temperature.

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

5. AIR CONDITIONING OPERATION
The A/C control assembly receives various signals, i.e., the engine rpm from the engine control module, out side air temperature signal from the A/C ambient temp. sensor, coolant temperature from the engine control module and the lock signal from the A/C compressor, etc.

When the engine is started and the A/C SW (A/C control assembly) is ON, a signal is input to the ECU. (built in the A/C control assembly).

As a result, the GROUND circuit in A/C control assembly is closed and current flows from HEATER fuse to TERMINAL 1 of the MG CLT relay --> TERMINAL 2 --> TERMINAL MGCR of the A/C control assembly --> 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. If the A/C control assembly detects the following conditions, it stops the air conditioning:
^ Evaporator outlet air is too 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 is too low.
^ Rapid acceleration occurs.