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
1.) Compressor, mount and drive.
2.) Evaporator and blower assembly.
Follow the refrigerant cycle to better understand how it works:
The compressor pumps hot low-pressure vapor refrigerant being cycled back from
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
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