Did you know that a properly functioning A/C system is also instrumental in helping to defrost your windshield on those cold, damp winter days? Your A/C system helps to dehumidify the air passing through the defrosting system enabling your windows to quickly clear and stay fog free.
Your car’s AC is basically a heat pump that uses a refrigerant to cool the air inside the car. It doesn’t create cold air. Instead, it removes the heat from the environment.
How Does my Car AC Work?
Your car’s AC system consists of an A/C Condenser, which can be found in front of the radiator, an A/C Compressor, which is attached to the engine, an evaporator core, which is behind your dashboard, an Orifice Tube or Thermal Expansion Valve, a Reciever/Dryer, and some plumbing. All of this is filled with a refrigerant gas, which is what actually cools the air, and an oil, which is dispersed in the gas to lubricate the inside of the system.
The A/C Compressor, as the name suggests, is a pump. It’s attached to your engine’s crankshaft by a belt, and uses a small amount of engine power to turn the pump and compress the refrigerant gas to help turn it into a liquid.
The A/C Condenser is like a radiator. It sits in front of your actual radiator, near the front of the car. The refrigerant enters the condenser as a pressurized gas from the compressor. The process of pressurizing the gas and moving it to the condenser creates heat, but the airflow through the condenser removes that heat until the gas becomes a liquid.
The Receiver/Dryer is the next stop for the refrigerant. It receives the now-liquid refrigerant, and moves it through a dessicant (like the silica gel packets you typically find in a box of new shoes) to remove any water that has found it’s way into the system.
The Thermal Expansion Valve or Orifice Tube is a restriction placed in the line after the Reciever/Dryer, just before the Evaporator Core. It’s an intentional restriction in the line that reduces the pressure on the liquid refrigerant so it’s ready to turn back into a gas. Sort of like what happens to the butane inside a BIC lighter when you press the thumb paddle.
The Evaporator Core is where the magic happens. It also looks like a radiator, with its coil of tubes and fins, but its job is to absorb heat rather than dissipate it. Refrigerant enters the evaporator coil as a cold, low-pressure liquid, ideally at 32 degrees Fahrenheit (0 degrees Celsius), which is why you don’t want any water in the system. The refrigerant doesn’t freeze at this temperature, but it does have a very low boiling point. The heat in the cabin of the car is enough to make the R-134a in the evaporator boil and become a gas again, just like water turning back to steam. In its gaseous form, refrigerant can absorb a lot of heat. The blower motor pushes air through the evaporator core, which cools the air, then through the evaporator box and out of the vents.
From there, the refrigerant flows back to the A/C Compressor so the cycle can continue indefinitely.
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