Heating and Air Conditioning: Description and Operation

1. HEATER BLOWER OPERATION

MANUAL OPERATION
When the blower control SW is set to any blower speed, the A/C ECU sends a signal to the blower motor control relay, and controls the speed of the blower motor.

AUTO OPERATION
When the auto SW is operated, the A/C ECU sends a signal to the blower motor control relay, according to the signals from each sensors and commands from the temperature SW, and controls the blower motor speed automatically.

2. AIR INLET CONTROL SERVO MOTOR CONTROL
When the FRESH/RECIRC select SW is switched to RECIRC, the motor in the air inlet control servo motor rotates to move the damper to the RECIRC side. The damper position is recognized by the TERMINAL TPI of the A/C ECU, and rotates the motor until the damper reaches its position.

When the FRESH/RECIRC select SW is switched to FRESH, the motor in the air inlet control servo motor rotates to move the damper to the FRESH side. The damper position is recognized by the TERMINAL TPI of the A/C ECU, and rotates the motor until the damper reaches its position.

3. AIR VENT MODE CONTROL SERVO MOTOR CONTROL
When the mode select SW in the instrument control panel is pushed, a signal is sent from TERMINAL MPX- of the instrument control panel to TERMINAL MPX+ of the A/C ECU, and activates the air vent mode control servo motor. This causes the servo motor to rotate to the position selected using the mode select SW (FACE, BI-LEVEL, FOOT, FOOT/DEF DEF), and moves the damper door.

4. AIR MIX CONTROL SERVO MOTOR CONTROL
When the temperature control SW in the instrument control panel is pushed, a signal is sent from TERMINAL MPX- of the instrument control panel to TERMINAL MPX+ of the A/C ECU, and activates the air mix control servo motor. The motor and damper door is moved until it reaches the temperature set by the temperature control SW.

5. AIR CONDITIONING OPERATION
The A/C ECU receives various signals, i.e.,the engine RPM from the crankshaft position sensor, outlet temperature from the A/C ambient temp. sensor, coolant temperature from the water temp. sensor, and the lock signal from the A/C compressor, etc. When the engine is started and the A/C SW in the instrument control panel is pressed, a signal is input from TERMINAL MPX- of the instrument control panel to TERMINAL MPX+ of the A/C ECU. As a result, the ground circuit in the A/C ECU is closed, and the current flows from the HEATER fuse to MG CLT relay TERMINAL 1 to TERMINAL 2 to TERMINAL ACMG of the engine control module to TERMINAL MPX2 to TERMINAL MPX1 of the body ECU to TERMINAL MPX2 to TERMINAL MPX+ of the instrument control panel to TERMINAL MPX- to TERMINAL MPX+ of the A/C ECU to TERMINAL E2 to GROUND, turning the A/C magnetic clutch ON so that A/C compressor operates. In addition, when the engine control module detects that the magnetic clutch is ON and the A/C compressor is operating, it controls the engine in the direction to avoid lowering the engine rpm during A/C operation.

When any of the following signals are sent to the A/C ECU, the A/C is turned OFF.
* Coolant temp. is high.
* Outlet air temp. is low.
* Large difference between the engine speed and compressor speed.
* The refrigerant pressure is abnormally high or low.