Like your vehicle's motor and transmission, the A/C is comprised of several components. Each has a exact job to perform in order to cool the cabin of your car. If any particular part fails, the whole assembly will either perform intermittently (e.g. Alternating cold and warm air), or stop working altogether. The challenge is narrowing down the culprit.
Identifying the root causes of problems you're experiencing with your air conditioner requires having a basic understanding of its operation. In this article, we'll take a brief tour through your car's A/C. I'll elaborate the role played by the personel components and recite a few reasons the assembly may be working poorly.
How The Assembly Works
The driving force is the compressor. It pushes pressurized Freon (type R134A) in a gaseous state into other component called the condenser. The condenser turns the gas into liquid form before sending it to the receiver-drier, other component in the system. The receiver-drier is where the liquid Freon is stored. It is also where moisture is removed (moisture can frost and cause an obstruction in the system).
The refrigerant remains pressurized within the receiver-drier until it is delivered to other component known as the thermostatic expansion valve. This is the point at which pressure is removed from the liquid Freon. It is then sent to the evaporator where it transforms back to a gaseous state.
Inside the evaporator, the chilled Freon absorbs heat from the cabin. At the same time, a blower fan pushed cold air into the cabin, cooling it. The refrigerant, still in gas form and now heated from the absorption process, is circulated back to the A/C's compressor. There, the cycle stars over.
Exploring potential Problems
The A/C's doing is simpler than it seems. Problems that affect its performance, while inconvenient, can normally be uncovered with a small investigative work.
One of the most tasteless culprits is a refrigerant leak; in fact, this is where most mechanics begin looking for a root cause for cooling issues. Leaks can occur in several places, along with the seals, hoses, O-rings, and the personel parts (e.g. Evaporator and condenser). As you would expect, the older your vehicle is, the more likely leaks will make due to general wear and tear.
Assuming there is no seepage of Freon throughout the system, diagnosing problems will depend on either there is no cool air or just an insufficient amount. If there is no cool air advent from your vents, the issue could be a failing drive belt, compression clutch, or a fuse that has blown. It might also be traced to a malfunctioning thermostatic expansion valve or a blockage somewhere in the system.
If you can feel cool air advent out of the vents, but it's not cool enough, the question might be connected to partial blockages, a failing compressor clutch, or even a low charge of Freon. It can also be due to a loose-fitting drive belt that's failing to adequately power the compressor.
In nearly all cases, problems with your vehicle's A/C are best left in the hands of an experienced mechanic. Not only is pressurized refrigerant dangerous, but a trained mechanic will have the diagnostic equipment needed to fast find the culprit.
Diagnosing Problems With Your Car's Air Conditioner