System Outline

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) or the A/C ECU (w/ LEXUS navigation system) sends signals to the blower control to adjust the blower motor speed.

Auto operation

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

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 TERMINAL TPI of the A/C control assembly (w/o LEXUS navigation system) or the A/C ECU (w/ LEXUS navigation system), the motor is continuously rotated until the damper reaches the 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 TERMINAL TPI of the A/C control assembly (w/o LEXUS navigation system) or the A/C ECU (w/ LEXUS navigation system), the motor is continuously rotated until the damper reaches the stop position.

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 on the mode select SW, and moves the damper.

When the temperature control SW on the driver's side is pressed, the A/C control assembly (w/o LEXUS navigation system) or the 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 on the temperature control SW on the driver side, and moves the damper. The passenger side can be operated in the same manner as the driver side.

The A/C control assembly (w/o LEXUS navigation system) or the A/C ECU (w/ LEXUS navigation system) 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 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) or A/C ECU (w/ LEXUS navigation system) comes on, a signal is input to the A/C control assembly (w/o LEXUS navigation system) or A/C ECU (w/ LEXUS navigation system).

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

If the A/C control assembly (w/o LEXUS navigation system) or A/C ECU (w/ LEXUS navigation system) detects the following conditions, it stops the air conditioning:

* The 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.