There you are, stuck in traffic and your air conditioning goes out. This can be a frustrating and uncomfortable scenario, but it can be handled so you can get back to driving in comfort. The first step to making sure your air conditioner is running properly is understanding the system itself. Here is a rundown of everything you need to know about your vehicle's a/c.
How the Automotive A/C Works
Here are the three main components:
Automotive air conditioning has been around for decades, but the system being used in most vehicles today is only about thirty years old. It consists of five basic parts: a compressor, an expansion valve, an evaporator/blower, a drier, and a condenser. This system circulates a refrigerant, which is a highly thermally-active substance that is pressurized and quickly expanded to make it cold. All automotive air conditioning works on the principles of compression and induction.
The pump, or compressor, resides on the engine as an accessory powered by the accessory/serpentine belt. When active, it pressurizes the refrigerant in the vehicle's a/c lines. There are two of those lines, the low and the high pressure. The side going into the compressor is the low pressure line and the side coming out of it is the high pressure side, for obvious reasons. The high pressure side will flow from the compressor to the condenser. The condenser is a type of radiator that takes the highly pressurized refrigerant through a series of switchbacks around which air flows, blowing off excess heat. This cooling action liquifies the refrigerant, which then goes to a drier.
The drier acts as an evaporator, separating water vapor from the refrigerant, reducing its freeze potential as a liquid that can enter the system through condensation, even though the system is closed, so the drier acts as a failsafe for that. From the drier, the refrigerant heads to the expansion valve. This valve opens and closes in a controlled way, causing the refrigerant to suddenly expand, or depressurize. The expanding refrigerant is sent through the evaporator as the sudden expansion causes it to get very cold. Air is passed over the evaporator (another type of radiator) as the refrigerant passes through.
Depressurized, low pressure, refrigerant hen goes through the expansion valve again, on the opposite side of the valve, and back to the compressor to complete the loop. The controls within the vehicle that turn the air conditioning on and off will open and close the expansion valve accordingly.
It should be noted that the refrigerant used in automotive air conditioning is considered a hazardous substance by governing authorities. It is illegal for anyone but qualified technicians to remove refrigerant.