Heating and Air Conditioning: Description and Operation

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The heater system uses a two-way-flow full-air-mix system that features high performance and low operating noise. It includes an independent face air blowing function and a cool air bypass function. The air conditioning (A/C) system is basically the same as the conventional system, but a new refrigerant system has been adopted as a response to restrictions on the use of chlorofluorocarbons.

OPERATION
When the air conditioning is working under low loads (e.g, in winter), the ECM or PCM controls the A/C compressor, condenser fan and idle-up speed more effectively, resulting in good fuel economy and quiet engine operation. In addition, the condenser fan will always run for five minutes as initial check after the battery is reconnected.

Condenser fan and radiator fan control
- For the operation of each fan, refer to Diagnosis.

Compressor control

When operating the air conditioning switch
- The automatic compressor controller stops the air compressor when the air thermo sensor detects a temperature of 3.2°C (38°F) or less. However, if the outside air temperature sensor detects a temperature of 10 - 20°C (50 - 680F), the controller stops the air compressor when the air thermo sensor detects 6.2°C (43°F) or less. Because of this control, the air compressor can work efficiently when the air conditioner is under low load.
- The ECM or PCM stops the air compressor when the engine coolant temperature sensor detects 115°C (239°F). In addition, the air compressor stops for five seconds when the accelerator position sensor input exceeds 80%. Moreover, the air compressor stops during engine start and low engine speed. Because of this control, the engine load can be reduced.
- The dual pressure switch turns OFF when the refrigerant pressure becomes excessively high or low, thus protecting the compressor circuit. (See Table)
- When these two sensors are all activated, the dual pressure switch is ON, and the ignition switch, blower switch, and air conditioning switch are ON, the A/C compressor relay is energized.

When operating the air outlet changeover control knob
- When the air outlet changeover control knob is moved to "DEFROSTER" or "DEFROSTER/FOOT" position, the micro switch, which is connected in series to the air conditioning switch, is turned ON. The other compressor control than the above is the same as that when operating the air conditioning switch.

A/C Compressor Relay ON Conditions: