Heating and Air Conditioning: Description and Operation

1. HEATER BLOWER OPERATION
Manual blower operation
When the blower control SW is set to any blower speed, the A/C control assembly operates and the current to drive the blower motor flows from TERMINAL BLW of the A/C control assembly to TERMINAL SI of the blower controller. The current activates the HEATER relay and the voltage applied to TERMINAL +B of the blower controller is output at TERMINAL M+ as the voltage for the selected blower speed. The current then flows from TERMINAL M+ of the blower controller to TERMINAL 2 of the blower motor to TERMINAL 1 to TERMINAL M- of the blower controller to TERMINAL GND to GROUND, and the blower motor operates at the blower speed selected.
Auto function
When the auto SW is turned on, the A/C control assembly calculates the required vent temperature based on the set temperature and input from each sensor. Then TERMINAL BLW of the A/C control assembly inputs current to TERMINAL SI of the blower controller in conformity with the required vent output. This current activates the blower controller so that current flows from TERMINAL M+ of the blower controller to TERMINAL 2 of blower motor to TERMINAL 1 to TERMINAL M- of blower controller to TERMINAL GND to GROUND, activating the blower motor. The blower motor then operates at different steps in conformity with variable current flow output from TERMINAL BLW of the A/C control assembly to TERMINAL SI of the blower controller.

2. OPERATION OF AIR IN LET CONTROL SERVO MOTOR
(Switching from FRESH to RECIRC)
With ignition SW turned on, the current flows from HEATER fuse to TERMINAL IG+ of the A/C control assembly to TERMINAL AIR to TERMINAL 1 of the air inlet control servo motor to TERMINAL 2 to TERMINAL AIF of the A/C control assembly to TERMINAL GND to GROUND, and 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 4 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 ignition SW turned on, when the RECIRC-FRESH SW is switched to the FRESH side, the current flows from HEATER fuse to TERMINAL AIF to TERMINAL 2 of the air inlet control servo motor to TERMINAL 1 to TERMINAL AIR of the A/C control assembly to TERMINAL GND to GROUND, and the motor rotates and the damper stops at that position.

3. OPERATION OF AIR VENT MODE CONTROL SERVO MOTOR
When the mode select SW in the A/C control assembly is pushed, the ECU in the A/C control assembly activates the air vent mode control servo motor. This causes the servo motor to rotate to the position (FACE, BI-LEVEL, FOOT, FOOT/DEF, DEF) selected using the mode select SW (A/C control assembly), and moves the film damper.

4. OPERATION OF AIR MIX CONTROL SERVO MOTOR
When the temperature control SW in the A/C control assembly on the driver's side is pressed, the ECU in the A/C control assembly sends a signal to the air mix control servo motor on the driver's side. This signal drives the motor to reach the temperature set by the temperature control SW (A/C control assembly) on the driver's side, and moves the film damper. Passenger's side is operated same as driver's side.

5. AIR CONDITIONING OPERATION
The A/C control assembly receives various signals, I.E., the engine RPM from the crankshaft position sensor, outlet temperature signal from the A/C ambient temp. sensor, coolant temperature from the engine coolant temp. sensor 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 into 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 to TERMINAL 2 to TERMINAL ACMG of the engine control module to TERMINAL MPX2 to TERMINAL MPX- of the A/C control assembly or engine control module to TERMINAL MPX1 to TERMINAL MPX- of the body ECU to TERMINAL MPX+ to TERMINAL 13 of the combination meter to TERMINAL 12 to TERMINAL MPX+ of the A/C control assembly to TERMINAL GND to GROUND, turning the relay on so that the A/C 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 and rotates the motor open direction to avoid lowering the engine RPM during A/C operation.
When any of the following signals are input to the A/C control assembly, the control assembly operates to turn off the air conditioning.
* Engine temp. signal is high.
* Coolant temp. signal is high.
* A signal that the temperature at the air outlet is low.
* A signal that there is a large difference between engine speed and compressor speed.
* A signal that the refrigerant pressure is abnormally high or low.