Air Conditioning

System Outline

1. Heater Blower Operation

Manual operation
When the blower speed is set to a certain level using the blower control SW, the A/C control assembly (w/o LEXUS navigation system), A/C ECU (w/ LEXUS navigation system) sends the signals to the blower control to control the blower motor speed.

Auto operation
When the auto SW is pushed, the A/C control assembly (w/o LEXUS navigation system), A/C ECU (w/ LEXUS navigation system) sends the signals from various sensors and temperature SW to the blower control to automatically control the blower motor speed.

2. Air Inlet Control Servo Motor Control
When the FRESH/RECIRC select SW is set to RECIRC, the motor in the air inlet control servo motor starts rotating to move the damper toward the RECIRC side. Since the damper position is detected by the TERMINAL TPI of the A/C control assembly (w/o LEXUS navigation system), A/C ECU (w/ LEXUS navigation system), the motor is continuously rotated until the damper reaches its stop position. When the FRESH/RECIRC select SW is set to FRESH, the motor in the air inlet control servo motor starts rotating to move the damper toward the FRESH side. Since the damper position is detected by the TERMINAL TPI of the A/C control assembly (w/o LEXUS navigation system), A/C ECU (w/ LEXUS navigation system), the motor is continuously rotated until the damper reaches its stop position.

3. Air Vent Mode Control Servo Motor Control
When the mode select SW is pushed, the A/C control assembly (w/o LEXUS navigation system), A/C ECU (w/ LEXUS navigation system) 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, and moves the damper.

4. Air Mix Control Servo Motor Control
When the temperature control SW on the driver's side is pressed, the A/C control assembly (w/o LEXUS navigation system), A/C ECU (w/ LEXUS navigation system) 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 on the driver's side, and moves the damper. Passenger's side is operated as same as the driver's side.

5. Air Conditioning Operation
The A/C control assembly (w/o LEXUS navigation system), A/C ECU (w/ LEXUS navigation system) receives various signals, I.E., the engine RPM from the engine control module, outside air temperature signal from the A/C ambient temp. sensor and coolant temperature from the engine control module, etc.

When the engine is started and the A/C SW (A/C control assembly (w/o LEXUS navigation system), A/C ECU (w/ LEXUS navigation system) ) is on, a signal is input to the A/C control assembly (w/o LEXUS navigation system), A/C ECU (w/ LEXUS navigation system).

As a result, the ground circuit in A/C control assembly (w/o LEXUS navigation system), A/C ECU (w/ LEXUS navigation system) is closed and current flows from IG1 fuse to TERMINAL 1 of the MG CLT relay to TERMINAL 2 to TERMINAL MGC of the A/C control assembly (w/o LEXUS navigation system), A/C ECU (w/ LEXUS navigation system) to GROUND, turning the MG CLT relay on, so that the magnetic clutch is on and the A/C compressor operates.

If the A/C control assembly (w/o LEXUS navigation system), A/C ECU (w/ LEXUS navigation system) 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.