Overview of Automatic Control
Overview of Automatic Control of Automatic Air ConditionerThe automatic air conditioner on this vehicle has the following features:
- Interior temperature control.
- Air flow control.
- Mode (blow port) control.
- Intake (switching between fresh air and interior air) control.
- Heater start timing control.
- Cooler start timing control.
- Evaporator anti-freeze control.
Automatic Air Conditioning System
System Overview (Chart)
Conditions both inside and outside the vehicle are detected by sensors (in-car temperature sensor, ambient temperature sensor, duct sensor, sun sensor, speed sensor, and water temperature sensor). These sensors send signals to the control unit.
Potentiometer position sensors send data to the control unit. Signals related to control panel settings are also sent to the control unit.
In response to the signals received, the control unit automatically adjusts air-mix door aperture (outlet air temperature), fan speed (forced air volume), and air intake (outside air, recirculated inside air, or a mixture of the two).
Interior Temperature Control
When the temperature control switch is set to a specific temperature, a signal is sent to the A/C control unit. Other signals are sent to the control unit from the various sensors. This data is analyzed by the control unit which creates a composite data signal that is compared with the signal received from the potentiometer. The result determines the direction of mix actuator rotation.
The mix actuator reacts to the composite air mix door opening angle signal. Opening angle is increased or decreased to maintain the temperature at the selected level.
When the compressor is off, the air mix door moves toward the COOL side. When the compressor turns on, the temperature of the air being discharged from the outlet vents is regulated.
When the temperature control is set to 18 °C (65 °F), the air mix door moves to the FULL COOL position. When the control is set to 32 °C (90 °F), the door moves to the FULL HOT position.
In the VENT position, the air mix door moves from FULL COOL to a 60% aperture. This prevents hot air from being discharged into the vehicle.
Air Flow Control
In the Auto Mode
- Automatic operation
When the AUTO switch or the DEF switch is pressed, a signal indicating the forced air volume is sent to the A/C auto-control unit. Other signals are sent to the control unit from the various sensors. This data is analyzed by the control unit which creates a composite data signal. Based on this signal, the base voltage of the power transistor is varied to change the blower voltage. This results in a non-stepped change in blower motor speed.
When the temperature control switch is set to either 18 °C (65 °F) or 32 °C (90 °F), blower motor speed is in the MAX-HI mode.
In the Manual Mode
- Manual operation
When the fan switch is manually set to a specified air volume, a signal is sent to the A/C auto-control-unit. In response to this signal, the auto-control unit controls the blower voltage.
When the fan switch is set to HI, the max-hi relay operates to increase blower motor speed to the MAX-HI mode.
Mode (Blow Port) Control
The A/C control unit receives temperature setting data as well as temperature and solar radiation level data from the various sensors. Based on this data, the control unit compiles a composite TMO signal. The TMO signal allows the outlet positions to be changed in a set pattern (VENT-->BI-LEVEL-->FOOT-->DEFROST/FOOT).
The mode actuator acts in response to mode position. It compares data signals received from the target mode, the door position, and mode door position to determine the direction of rotation.
If the temperature is set to 18 °C (65 °F), cool air is discharged from the head outlets. If the temperature is set to 32 °C (90 °F), warm air is discharged from the foot outlets.
In manual mode, existing air outlet settings remain unchanged when the temperature is set to 18 °C (65 °F) or 32 °C (90 °F).
Mode switch operation
Press the mode switch to change to the outlet mode. Blower operation (outlet mode position) can now be switched between the VENT, BI-LEVEL, FOOT, and DEF positions.
Defroster switch operation
The DEF position can be selected from the outlet mode.
Intake (Fresh air/interior air switching) Control
During automatic operation, the A/C control unit responds to the temperature setting signal together with signals from the various sensors to generate a general signal that controls operation in a prescribed pattern.
If either or both the fan and the cooler are off, air intake is from outside the vehicle.
If the temperature control switch is set to either 18 °C (65 °F) or 32 °C (90 °F), the air inside the vehicle is recirculated.
1. Manual switch operation
Press the intake switch to change between outside air intake and recirculated inside air.
2. Defrost switch operation
Air intake is from outside the vehicle.
3. Mode switch operation
During automatic operation, outside air intake or recirculated inside air is selected as appropriate.
During manual operation or when the DEF mode is selected, air intake is from outside the vehicle.
Compressor Control
In the automatic control mode, the automatic air conditioner control unit turns on or off the compressor with the evaporator anti-freeze mechanism using the evaporation sensor. And, when outside air is detected to be low through the outside air temperature sensor signal, the control unit turns off the compressor using the compressor control function.
Manual Control
- In the automatic control mode, pressing the A/C (air conditioning) switch turns off the compressor.
- Pressing the DEF mode switch automatically turns on the compressor.
Heater Start-up Control
Heater start-up control occurs when the air discharge mode is in the BI=LEVEL, FOOT, or DEF/FOOT position and the heater core temperature is less than 14 °C (58 °F).
Air discharge volume remains in the AUTO LO mode until the engine coolant temperature rises above 14 °C (58 °F). The volume then increases in linear increments to the pre-set level.
Cooler Start-up Control
When cooler operation is started with the air discharge mode is in the VENT or B/L position and the in-car temperature higher than 26 °C (78 °F) (detected by the in-car sensor), cooler start-up control occurs.
For the first 7 seconds of cooler operation, the fan remains OFF. It then switches to AUTO LO. Air discharge volume then increases in linear increments to the pre-set level.
Cooler start-up control occurs the first time the engine is started or the cooler switch is moved from OFF to AUTO. It will not occur during subsequent switch movements.