Heating and Air Conditioning: Description and Operation

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GENERAL DESCRIPTION
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. In addition, an air purifier which carries out fine A/C control has been included.

OPERATION

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

Compressor control
When operating the air conditioning switch
The air thermo sensor, which senses the temperature of the air flowing out of the evaporator, deactivates the compressor at 5°C (41.0°F) or below.

A/C Compressor Relay ON Conditions:

The dual pressure switch turns OFF when the refrigerant pressure becomes excessively high or low, thus protecting the compressor circuit.

When the air thermo sensor is 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 defroster 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.

When compressor locks
Since the compressor and alternator are driven by the same belt, the electric generating function of the alternator also stops when the belt is broken. In order to assure the electric generating function of the alternator, there is an A/C-ECU to prevent breaking of the belt due to slipping when the compressor locks. The A/C-ECU makes a comparative calculation of the compressor revolutions and the engine revolutions which are detected by the revolution pick-up sensor. When 70% or more slip ratio continues for 3 seconds or more, the A/C compressor relay goes from on to off; at the same time, the operation display in the air conditioner switch blinks to announce an abnormality.