This was originally my response to a post on another forum, but then I decided to share it with our members here... and so begins part one in a series of auto a/c articles I propose to write.



Mobile air-conditioning systems consist of five refrigeration circuit component groups:

1.) Compressor, mount and drive.
2.) Evaporator and blower assembly.
3.) Condenser.
4.) Hoses.
5.) Drier/accumulator.

Follow the refrigerant cycle to better understand how it works:
The compressor pumps hot low-pressure vapor refrigerant being cycled back from the evaporator.
In the compressor, the refrigerant changes state as the low-pressure vapor is compressed in to a high-pressure vapor and then pumped into the condenser.
The high-pressure vapor is hotter than the outside, (ambient) temperature and this additional heat is removed as it passes through the condenser.
As the high-pressure vapor temperature drops, it changes state again, and condenses into a high-pressure liquid and is passed on to the drier where it is filtered, dried, and stored. A pick up tube in the bottom of the drier assures that a solid stream of vapor less liquid refrigerant is passed to the expansion valve.
The expansion valve, via a fixed or variable orifice, regulates the flow of high-pressure liquid refrigerant into the evaporator.
The pressure of the evaporator is roughly ten times lower than that of the high-pressure liquid at the expansion valve inlet allowing the refrigerant to expand quickly and boil.
As the refrigerant flows though the evaporator coils, forced air is being blown across the evaporator fins from the blower motor, the low-pressure vapor expands, boils and absorbs heat from the passenger compartment.
This action results in cooler air being routed through the distribution box and on the dash vents.
The hot low-pressure vapor is passed on to the compressor to cycle through the system again.