What are the Components of any Air Conditioning System?

• Thermostat - A thermostat is a temperature sensitive device, which when activated, signals the electromagnetic compressor clutch to engage.
   
• Compressor(s) - The compressor is the belt-driven, high-pressure pump, which circulates the refrigerant through the evaporator and condenser.  The operation of the compressor is controlled by an electromagnetic clutch, which in turn, is controlled by a thermostat.
   
• Electromagnetic Clutch - The electromagnetic clutch controls the operation of the compressor.  When engaged, the compressor circulates refrigerant and provides cooling.
   
• Condenser(s) - The condenser is located in the skirt or on the roof of the vehicle.  Its primary function is to reject heat, which was transferred to the refrigerant, by the evaporator, from the passenger compartment of the vehicle.
   
• Filter Drier - Removes moisture and particulate matter from refrigerant.
   
• Expansion Valve - Meters refrigerant into the evaporator coil.
   
• Evaporator(s) - The evaporator is located in the interior of the vehicle.  Its primary function is to transfer heat contained in the passenger compartment air, into the refrigerant, which is circulated by the compressor, through the evaporator coil.  During this process, the air is also filtered and dehumidified.
   
• Refrigerant - A refrigerant is any material which possesses high heat transfer capabilities.  Its primary function is to act as the medium for heat transfer, which facilitates the movement of heat from the passenger compartment to the outside air.  Refrigerant under varying pressures exists in different states, and performs different heat transfer functions.  Under low pressure, refrigerant exists as a gas which can absorb heat.  Under high pressure, refrigerant exists as a liquid which can reject heat.  The heat transfer properties exhibited when refrigerant changes state, is the foundation of the refrigeration cycle.

What is the refrigeration cycle?

• The thermostat, located in the interior of the vehicle, calls for cooling.
• Based on a signal from the thermostat, the electromagnetic clutch on the compressor engages, circulating refrigerant through the system.
• Refrigerant existing as a gas, and containing the heat from the passenger compartment is pumped by the compressor under high pressure into the condenser coil.
• Fans pull cool air through the condenser coil, which contains refrigerant existing as a hot gas.
• The refrigerant undergoes a change-of-state, from a gas to a liquid, through a process called condensation.
• During condensation the hot gas rejects its heat load to the outside air, which was transferred from the passenger compartment, into the refrigerant, by the evaporator.
• The refrigerant now exists as a cool liquid, which passes through the filter drier, which removes moisture and impurities, and then the sight glass, which enables visual inspection of the refrigerant.
• The cool liquid is then pumped to the evaporator where an expansion valve meters the refrigerant into the evaporator coil.
• Fans pull passenger compartment air through a filter, which removes particulate matter and then passes the cleaned air through the evaporator coil.
• The refrigerant undergoes a change of pressure from high to low, and a corresponding change-of-state from liquid to gas, through a process called evaporation.
• During evaporation, the heat contained in the air in the passenger compartment is absorbed by the gaseous refrigerant.
• As warm air passes through the evaporator coil, moisture condenses, and is collected and drained to the exterior of the vehicle.
• The hot gas is then suctioned back to the compressor and pumped to the condenser to repeat the cycle.

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