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Auto Air Conditioning

Learn the basics of how auto air conditioning systems operate, and what to do when problems occur.

Auto air conditioning is important to an enjoyable driving experience. [©Jupiter Images, 2009]
©Jupiter Images, 2009
Auto air conditioning is important to an enjoyable driving experience.

Auto Air Conditioning

Many people take their auto air conditioning for granted. They assume that when they hit the air conditioning button, refreshing cold air will flow out of vents into their cars. Auto air conditioning is a major convenience that keeps drivers comfortable in the hot summer months.

But what happens when the air conditioner stops working? Sometimes it pumps out less cold air than usual, and sometimes it stops working entirely. When this happens, it becomes obvious how much drivers rely on auto air conditioning. To understand what happens when an auto air conditioning system breaks down, drivers should understand how the system works.

Basic Components of an Auto Air Conditioning System

Auto air conditioning systems operate using the principles of condensation and evaporation. Both evaporation and condensation happen at normal air pressure. However, a higher pressure can change vapor into liquid, as explained at Edmunds, Inc. Auto air conditioning systems use this higher pressure to create the blasts of cold air that drivers have come to depend on.

An auto air conditioning system is made up of six parts:

  • The refrigerant, a liquid that can vaporize at a relatively low temperature. Older cars used R-12 refrigerant, which contained CFC and was harmful to the environment. Today's cars use an eco-friendly refrigerant called R-134A.
  • The compressor, which is the power unit of the air conditioning system. It pumps highly pressurized refrigerant vapor to the condenser.
  • The condenser receives the refrigerant vapor and changes it into a liquid.
  • The receiver-drier removes moisture from the refrigerant and stores it. If moisture remains in the refrigerant, it can freeze and cause a blockage in the system.
  • The thermostatic-expansion valve removes the pressure from the refrigerant, allowing it to turn back into a vapor.
  • The evaporator, which is made up of tubes and fins, absorbs heat from the passenger area of the car while the cooler air blows out. Then the cycle begins again.

Identifying Problems with Auto Air Conditioning Systems

Auto air conditioning systems are generally reliable. When things do go wrong, it's usually one of two problems: the amount of cool air is insufficient or there's no cool air at all.

A complete lack of cool air could be due to a number of factors, including:

  • A blown fuse
  • A broken or loose drive belt
  • Clogs in the expansion valve, the receiver-drier or the liquid refrigerant line
  • A defective expansion valve
  • An inoperative compressor
  • A leaking component in one of the parts, hoses or seals
  • A slipping compressor clutch

Insufficient cool air could be caused by some of the same defects as well as these:

  • A clogged condenser or evaporator
  • Leaks
  • Low refrigerant charge
  • A partly clogged filter or expansion valve

At-Home Repairs

Car owners can take several troubleshooting steps if their auto air conditioning system stops working properly, according to Trust My Mechanic.com. First, they can check to see if the fan motor near the condenser is on. If their model is equipped with a fan blade, the blade should be rotating very quickly.

Overheating can also cause air conditioning problems. In some cars, both the air conditioner condenser and the radiator have cooling fans. Auto owners should check to make sure both of these fans are working. A car sitting idle on a hot day with the engine running should be using both fans.

Car owners can take steps to prevent future auto air conditioning problems from occurring. For example, routine maintenance and having the system checked on a regular basis can keep the air conditioner running smoothly. In addition, some technicians recommend that car owners run their auto's air conditioning unit for at least 10 minutes per month, even during the cold season. The refrigerant contains a light mineral oil that keeps the compressor lubricated, but the system needs to run regularly in order for the oil to be beneficial.

When to Take the Car to a Mechanic

Unfortunately, most auto air conditioning problems can't be fixed at home. If the at-home troubleshooting tips don't fix the problem, consumers should take their cars to a certified mechanic. The mechanic can check for leaks, clogs, loose or broken parts and blown fusesand fix whatever is broken so that the auto air conditioning system works again. Some repairs, such as replacing the drive belt or recharging the refrigerant, use special equipment that can only be found at a repair shop.

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