Automotive Air
Conditioning
It seems only a few years ago air
conditioning was a real luxury. Very few cars came with air conditioning installed from
the factory. The garage where I first worked, installed 'add on air' Now it's rare
for a new car not to have air conditioning.
Basic maintenance is about the same as the cooling system; clean leaves and bugs from the
front of the car. good air flow is very important.
It seems to be a good idea to use the air
conditioner in the winter to help defrost the windshield. (Not all cars do this
automatically) Use the air conditioner at least once per week if possible.
Some loss of freon after a few years may be 'normal'
Seals wear and loose pliability after being subjected to heat and vibration. Under
hood temperatures "cook" hoses and coupling seals.
We suggest an air conditioning "check up" at the
first sign of diminished cooling.
Anatomy of an automotive air conditioner
Compressor Image
The 'heart' of the system, pumps refrigerant
through the air conditioning system. Refrigerant (freon) is a hot gas when it leaves the compressor
and must be cooled and allowed to 'condense'
to a liquid state.
Condenser
Image
The hot gaseous freon goes from the compressor to the condenser. The condenser
looks similar to, and is mounted in front of the radiator. Air flowing through the
condenser cools the freon. The freon gives up heat to the air and changes to the liquid
state. From there it flows to the
receiver-drier.
Receiver / drier
Image
The liquid freon is "stored" in the receiver-drier
for a time
until it flows to the expansion valve. While being stored, the
freon comes in contact with a desiccant material that removes moisture that may be in the
system. Freon must be dry. Water
and freon molecules can combine to form acids that do
damage to the system.
Expansion valve
Image
The expansion valve controls the
amount of freon flowing into
the evaporator. Like a water valve,
it controls the flow of liquid.
The amount of freon allowed to enter controls the temperature
in the evaporator.
Evaporator
Image
The evaporator looks somewhat like
a small radiator. Liquid
freon, under high pressure, is metered into the evaporator
(which is at a much lower pressure) and allowed to change
from a liquid back to the gaseous state. The blower motor
directs the air inside the cab across the evaporator. Heat is
removed from this air when this change of state occurs, cooling
the inside of the vehicle.
Diagram courtesy Marshall Brian howstuffworks.com |
