Most all new cars that are sold now are equipped with an air conditioning (A/C) system, with most of us relying on it every single day, depending on where we live and the surrounding climate. Thankfully, there are very few problems with the sophisticated, modern systems of today, however, every A/C will need some type of maintenance at some point, and after a few years of service, most will need new refrigerant added as well.
The two most common complaints about air conditioning in cars is that the system is either producing not enough cold air, or no cold air at all. Neither case means that the entire system is damaged or must be replaced, but rather a series of diagnostic checks should be made to determine the exact root of the problem and if any parts do need replacing or repaired.
Understanding Automotive Air Conditioning
A car's air conditioner is comprised of six main components, the compressor and condenser, an evaporator, the receiver-drier, a thermostatic expansion valve, and the liquid refrigerant. Having a basic understanding as to how each of these work will help when it comes time to locate the source of a problem or when having it repaired.
The compressor is what actually powers the system and is driven by belt that is connected to a part of the car's engine. The compressor then emits vapors from the liquid refrigerant using high pressure and heat sent to the unit's condenser. The A/C condenser then changes the vapors to liquid before it moves on to the area known as the receiver-drier, which not only serves as a type of storage tank for the refrigerant in its liquid state, but removes excess the moisture from the refrigerant as well.
The liquid refrigerant is then sent to the unit's thermostatic expansion valve that works to remove all of the pressure, allowing it to expand and turn into a vapor as it flows through the evaporator, which is rather similar to the condenser. After the low pressure refrigerant is sent to the evaporator it is vaporized and works to absorb all of the existing heat from the air inside the car's passenger compartment. Once all of the heat is absorbed, the air remains cool and is circulated throughout the inside with the help of a blower fan.
System Performance Tests and Checking for Leaks
Although a system performance test is not an actual repair itself, it is still vitally necessary along with an initial evaluation in order to determine the actual cause for the air conditioning system's poor performance. The final repairs made will ultimately depend on the diagnostic tests used, which may be as simple as a visual inspection of the system.
An air conditioning system performance test will involve first checking the temperature of the air coming from the vents to ensure that it is below the normal levels. If so, the mechanic or technician will then perform what is known as a head pressure check in which gauges are used to determine the level of refrigerant in the system.
Low pressure readings, or the absence of pressure at all, will indicate that there is usually a leak somewhere that must be located and repaired before adding more refrigerant, which thanks to the Clean Air Act enacted by the U.S. federal government, no longer contains chlorofluorocarbons that we now know to be extremely harmful to the atmosphere's delicate ozone layer.
While it is completely normal, and even necessary, for a car's air conditioner to lose some of its refrigerant, larger leaks will cause a noticeable loss of performance. If diagnostic tests do reveal either low or no pressure coming from the system, a technician must scan it to locate the problem area and ascertain if the leak is liquid or gas refrigerant and which components must be replaced.
Pressure readings during the system performance test that are too high may indicate a blockage or restriction somewhere that is preventing the refrigerant from flowing properly. In most cases, small pieces of dirt have found their way into the small tube that's in place to filter out debris and must be flushed out in order to restore the flow of air through the vents.
All automotive air conditioning systems now must use what is known as R-134A, which is an environmentally friendly refrigerant. Those vehicles made before the year 1996 may still be using the old chemical called R-12 and by law, their A/C systems must be converted or refitted in order to be able to receive the newer refrigerant. All new valves must be installed as well as a complete flushing and cleaning to remove all remnants of the old refrigerant as mixing the two substances will irreparably damage the system and its components.