Air Conditioning System
The purpose of the Air Conditioning (AC) System is to keep you and your passengers comfortable (cool and dry) as you drive, mostly during hot and humid summer days. This system is now a standard feature on most recent vehicles.
Our Autotech Performance technicians can effectuate the periodic maintenance service and repairs work required to ensure the optimal functioning of your vehicle’s AC system.
Air Conditioning System Main Components
- A/C Control Panel
- Expansion Valve
How does the Air Conditioning System work?
In the air conditioning system, the compressor acts as a pump and pushes freon – a refrigerant – through the system when you switch the AC “on” by turning the knob on the AC control panel. The gaseous refrigerant reaches the condenser which dissipates the heat absorbed by the freon and turns it into a liquid state. The refrigerant then goes toward the receiver/dryer where it is cleaned and dried. From there, the freon is directed toward the expansion valve which controls its flow into the evaporator and transforms it from liquid to gas state. The gaseous freon then circulates through the evaporator. The air from the passenger compartment is blown by the fan toward the evaporator where its heat and moisture are absorbed by the circulating freon that turns into a liquid again. The thermostat, located inside the evaporator housing, prevents the evaporator from freezing by cycling the compressor on and off.
The compressor is usually a multicylinder pump. It is driven by a belt from the engine main pulley and turns at roughly the same rpm as the engine. The compressor circulates gaseous freon at a constant pressure regardless of the engine rpm. Indeed, a clutch on the compressor allows the latter to be disconnected from the drive pulley when the refrigerant temperature reaches the thermostat’s preset level – to avoid freezing within the evaporator. The compressor clutch is also deactivated under heavy loads to ensure that more power is available to the engine when needed.
Freon is a substance with very high heat absorption properties. As a liquid, freon is very cold – around 150 degrees below zero Fahrenheit. There are several kinds of freon. New vehicles (1994 and up) use “freon 134” – instead of “freon 12” – because it does not contain chlorofluorocarbons or CFCs. The change was done in order to eliminate causes of the ozone layer depletion. Note that different types of freon are not interchangeable.
The A/C control panel located on the dashboard allows you to regulate the temperature and direction of the air flow from the air conditioner system.
As freon goes through the condenser, it is cooled down to a liquid state. The receiver/dryer is a canister through which liquid freon circulates to get cleaned and dried. The receiver/dryer contains a desiccant that dries the freon and a charcoal filter that eliminates its moisture. The sight glass, used to view the level of refrigerant in the AC system, is usually located at the receiver/dryer.
The expansion valve has a very small hole through which freon is forced, causing it to become a gas as it enters the evaporator. The opening of the valve is regulated by the temperature of the freon circulating through the evaporator. If the thermostat, located within the evaporator housing, indicates that the temperature and pressure of the refrigerant are too high, the valve restricts the flow of freon coming in, hence lowering its temperature and pressure.
The evaporator is located under the dashboard on the right side. It is a small radiator-like device that circulates gaseous freon. A fan blows air from the passenger compartment through this small radiator. As air passes through, the freon removes its heat and vents the moisture to the ground.
The thermostat also prevents the evaporator from freezing by cycling the compressor on and off. The condenser dissipates heat absorbed by the freon. It is located in front of the radiator, and is cooled by the two radiator fans.
Advice to optimize the use of your vehicle’s Air Conditioning System
- For rapid cooling and dehumidifying of the passenger compartment, you should set the controls as follows: Air vent open – Cold air – Fresh air – A/C on – Fan on high
- After 5 minutes or so, reset the controls to: Air vent open to suit yourself – Temperature to suit yourself – Fresh air – A/C on – Fan on low
- For rapid defrosting of your vehicle, you should set the controls as follows: Defrost on – Hot air – Re-circulated air – A/C on – Fan on high
- The A/C system should be checked periodically for leaks. The A/C system is tightly sealed due to a small amount of oil circulating through the system that keeps the seals soft and efficient. The lack of use of the A/C system causes leaks to develop as the seals dry up and crack. Therefore, as a prevention measure, you should run the A/C system for at least several minutes weekly, year round.
- The freon does not require periodic changing.
Signs of Troubles related to your vehicle’s Air Conditioning System
- Air output not cold
- Air volume low
- Belt squealing
- Fluid (other than water) leaks
- Noise in A/C compressor
- Squealing noise at startup