Heating and Air Conditioning: Description and Operation

AIR CONDITIONER OPERATION

NOTE: THIS VEHICLE DOES NOT USE CODE DRIVEN HVAC DIAGNOSTICS.

WHEN THE DIFFERENCE BETWEEN THE ENGINE AND COMPRESSOR SPEED IS EXCESSIVE, THE AMPLIFIER TURNS ON THE A/C SWITCH INDICATOR LIGHT TO INDICATE A FAULT.

WHEN THE BLOWER SWITCH IS SET TO ON, CURRENT FROM THE 30A HEATER/CB FLOWS THROUGH TERMINAL A14 OF THE A/C SWITCH, TERMINAL 1 OF THE A/C DUAL PRESSURE SWITCH TO TERMINAL 2 THEN TO TERMINAL 14 OF THE A/C AMPLIFIER,THEN TERMINAL 1 OF THE MAGNETIC CLUTCH RELAY VIA THE A/C FUSE. THE ENGINE SPEED SIGNAL FROM IGNITER, THE EVAPORATOR TEMPERATURE SIGNAL FROM THE A/C THERMISTOR, AND THE LOCK SIGNAL FROM THE A/C COMPRESSOR ARE ALL SUPPLIED TO THE A/C AMPLIFIER.

WHEN THE A/C SWITCH IS TURNED ON, THE A/C SWITCH ON SIGNAL IS SENT TO THE A/C AMPLIFIER, ACTIVATING IT AND TURNING ON THE MAGNETIC CLUTCH RELAY, SO THAT CURRENT FLOWS FROM TERMINAL 1 OF THE RELAY TO TERMINAL 2 A/C MAGNETIC CLUTCH, CAUSING THE COMPRESSOR TO OPERATE.

THE A/C OPERATION IS SHUT OFF WHEN A SIGNAL INDICATING LOW EVAPORATOR TEMPERATURE, GREAT DIFFERENCE BETWEEN THE ENGINE AND COMPRESSOR SPEEDS, HIGH WATER TEMPERATURE SIGNAL OR ABNORMALLY HIGH OR LOW REFRIGERANT PRESSURE, IS SUPPLIED WHILE THE ENGINE HIGH SPEED SIGNAL EXISTS. WHEN ONE OF THESE SIGNALS IS RECEIVED, THE AMPLIFIER SHUTS OFF THE A/C OPERATION.