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All About Air Conditioning
Courtesy Tire's expert technicians have the ability to service and repair your car's air conditioning system no matter what the problem may be. Whether your system is just not as effective as it used to be, or the system just doesn't work at all you can be sure that we'll get it fixed right and working as good as new for you in no time at all.


While most people think of air conditioning as a way to add cool air to the inside of your car, would you be surprised to know that in actuality air conditioning systems actually remove heat from the passenger compartment and the cool air you feel blowing at you is a bi-product of the heat transfer happening inside the air-box behind your dashboard?


In relatively simple terms, air conditioning is a process of removing heat from one source (the inside of your car) by way of a thermally conductive gas. In our case freon. That freon then moves the heat to another part of the system to release that heat energy to the atmosphere before returning once again to the passenger compartment to absorb more heat, and so the cylce goes.


Air Conditioning Sytem Diagram

The obvious first component of an air conditioning system is the freon itself which is the work horse that carries the heat from one area to the other. Freon is a very efficient thermally conductive gas which simply means it can abosorb and release heat energy very effectively. There are a number of different types of freon, but in automotive applications only R-134A has been used since 1995. Prior to 1995 R-12 freon was used, but was later banned in the production of new model vehicles due to it's ozone depleting effects when released into the atmosphere. R-134A isn't as efficient as R-12 in it's ability to transfer heat, but is environmentally friendly and much more cost effective to the consumer.

The next major component is the A/C compressor, which is the pump that pushes the freon through the system. As the freon leaves the A/C compressor it is in a state of high pressure, hot gas. At this point, the freon enters the condensor which looks a lot like your cars radiator and is most often mounted directly in front of the radiator. As air flows across the condensor it gradually cools the freon down to make it condense into a high pressure liquid. The condensor is also the area where all of the heat that has been absorbed in the passenger compartment is released as air moves over it's cooling fins.

The next stop for our freon is the reciever drier, also called an accumulator on some systems. Both serve the same function but are located on opposite sides of the system. The drier or accumulator serves two main functions. First is it's ability to store liquid refrigerant. As we'll discuss in the next step, the freon will change states again into a low pressure liquid by way of a restricting device that in most cases changes the size of the restriction in the system based on demands of the system to keep it in equilibrium. The drier/accumulator gives that freon a place to hang out until it is needed further down the line. Reciever driers also serve another function in removing any water from the freon. Water and freon mixed together create a corrosive compound that will eat away at the metal components of the system, so it's important that it be removed. This is also why it's critical to change the reciever drier anytime the system has to be opened for any reason. The desiccant material inside the drier is only sufficient to hold a couple of drops worth of water which is an easily attainable amount from just the atmosphere when the system is opened up.

As the freon moves further down the system, it now enters the expansion valve. An expansion valve is a neat little device that acts as sort of the general manager for the entire system. As the high pressure liquid freon enters the valve it passes through an orifice that can vary in size depending on the demands of the system. The result is that the freon moves from being a high pressure liquid to a low pressure liquid. The expansion valve also acts as the over all pressure regulator of the system as it changes the size of the orifices where the freon is going into the evaporator core and the freon coming out of the evaporator core to maintain the optimum pressure at which the freon can most effectively do it's job. From the output side of the compressor to the orifice in the expansion valve is what we call the "high side", or high pressure side of the system.

Once the freon leaves the expansion valve it flows into the evaporator core. The evaporator core is like a miniature radiator located in the air box behind your dashboard. As the hot air from the inside of your car moves accross the core, the freon moving through it absorbs the heat to be carried away leaving you with crisp cool air inside the car. We also have another change in the state of the freon at this point. As it absorbs the heat, it moves from a low pressure liquid to a low pressure gas much like water evaporating as you heat it up. The freon then carries that heat out of the evaporator core, passing through the expansion valve once again (through a seperate low pressure passage).

Lastly, this low pressure hot gas move out of the low pressure side of the expansion valve back into the suction, or inlet side of the compressor to start the cycle all over again. From the inlet of the evaporator core to the inlet of the compressor is what we call the "low side", or low pressure side of the system.


In most cases it is considered normal to lose up to 1/2lb. of freon per year through sweating of the rubber hoses and losses at fitting connections. When you consider that most automotive applications hold anywhere from just over 1lb. to 2lbs. of freon, you can see how your system can start to lose it's effectiveness relatively quickly. Courtesy Tire recomends having your system serviced once a year to ensure that you're not only maximizing the benefits of your A/C system, but the freon in your system also carries the lubricating oil for all of the components within the system and the less freon you have, the less oil is getting to critical components which can cause more costly repairs down the road.


Your air conditioning system does more than just cool the inside of your car during the summer months. During the winter, your vehicle runs the A/C anytime you have the defroster on. Because a natural by-product of running the A/C is to pull moisture out of the air, running the A/C while blowing warm air accross your windshield will draw the moisture that created the "fog" out of the air making your defroster much more efficient at clearing your windshield faster.
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