A/C System - Manual

DESCRIPTION
The A/C system consists of:






OPERATION
The A/C system allows temperature control by delivering heated or cooled air to maintain a constant comfort level. In addition, during A/C operation, relative humidity inside the vehicle is reduced. Controls are provided to adjust the temperature and system functions, including A/C blower motor speeds for desired air flow. Outside air is drawn from the cowl air inlet below the windshield during all system operations; except for MAX A/C cooling and OFF when recirculated air is used. Manual temperature control can be maintained in all control settings except when the system is turned off.

The air conditioning and the heating and defrosting systems use the same controls for air flow, temperature, and A/C blower motor speed. These controls are located in the Integrated Control Panel (ICP). Turn the function selector switch to A/C or MAX A/C to activate the air conditioning system.

System Block Diagram:

When the A/C function is selected, the Constant Control Relay Module (CCRM) closes. The CCRM then supplies current to the A/C clutch field coil which magnetically draws the A/C clutch in and locks it to the A/C clutch pulley. The engine then drives the A/C compressor. The A/C compressor pumps low-pressure gaseous refrigerant from the suction accumulator/drier, compresses it, and moves it into the A/C condenser core, where it cools and liquefies. The liquid refrigerant then passes through the A/C evaporator core orifice which restricts the refrigerant's flow and reduces its pressure before it enters the A/C evaporator core.

Since the refrigeration cycle is capable of producing more cooling than the air conditioning system needs, it must be controlled. Operation of the A/C compressor is interrupted to ensure the correct amount of refrigerant is circulated for air conditioning system operation. As refrigerant is pumped from the low-pressure side, the pressure gradually decreases until it reaches 159 ± 7 kPa (23 ± 1 psi). At this point, the A/C cycling switch and the CCRM open, thereby de-energizing the A/C clutch field coil and opening the A/C cycling switch. High-pressure refrigerant gas on the discharge side of the A/C compressor will continue to pass through the A/C condenser core and the A/C evaporator core orifice. When the A/C compressor is stopped, heat transfer from the circulating air to the evaporator refrigerant causes the refrigerant pressure in the low-pressure side to increase. When the pressure reaches approximately 317 kPa (46 psi) the A/C cycling switch and then the CCRM close, energizing the A/C clutch field coil and starting the A/C compressor again. This completes the clutch/pressure cycle.

Also, when head pressure rises to approximately 3068 kPa (445 psi), the A/C pressure transducer opens. The CCRM then opens, thereby de-energizing the A/C clutch field coil and stopping the A/C compressor. When head pressure falls to approximately 1724 kPa (325 psi), the A/C pressure transducer closes. The CCRM then closes, energizing the A/C clutch field coil which starts the A/C compressor.