Compressed Freon by A/C Compressor Makes Your Ride Cool
The Air Conditioning Compressor is the most important part of the AC system. As the AC Compressor compresses the Freon into near liquid state, it becomes a cool gas under high pressure. As it passes through the A/C condenser, it is cooled even further and becomes a liquid. The liquid flows through the drier (also referred to as an accumulator) into the evaporator core, where it absorbs heat and boils (Freon has a very low boiling point). Before the Freon starts to boil, it is very cold and condensation occurs and is drained away (which is the clear liquid you see under the car when the AC is on). As the Freon boils, it absorbs heat from inside the vehicle. The Freon gas is sucked back into the A/C Compressor, making the line from the evaporator to the compressor the low pressure side of the system. The drier traps any moisture that may occur during the heating/cooling process inside the line and the expansion valve controls the flow of Freon so the cooling effect is maximized, taking into account the outside temperature. There are also pressure limit switches, both low and high so the compressor is not damaged. The diagram below shows the sequence.
Refrigerant of Air Conditioning System
R12 refrigerant was used in cars for many years, but it was determined to be an ozone-depleting chemical and purchase is now restricted by Federal law (enacted November 1992). The sale of bulk containers was allowed until 1994. Currently, you must be certified as a professional AC technician to purchase it.
R134a replaced the R12 Freon that was used in most pre-1994 vehicles. Some people feel it does not cool as well as the old R12, but it is much more environmentally friendly. It is not illegal to have or use R12, but it is illegal to sell to non certified people. Some of the replacement R12 products are highly flammable and you should look for an EPA approved label on these products. R134a is NOT compatible with R12, so they should never be mixed. There are many kits available to convert the old R12 systems to R134a, but if there is any R12 left in the system it should be evacuated by a qualified technician and not discharged freely into the air.
Causes of Bad A/C Compressor
There are many reasons an Air Conditioning Compressor can go bad. The clutch pulley assembly that is mounted on the front can go stop working. There are 3 parts to this, the clutch, the coil and the pulley. Individual parts are sometimes available, but not for all models. The internal workings can fail, there are many mechanical parts that can simply wear out or break. Parts to rebuild an Air Conditioning Compressor are not available to the general public. The system can be overfilled (or filled incorrectly) and cause the system to seize, such as if too much Freon is put in the system or liquid is put where there should be gas. This will cause immediate failure. When an AC Compressor is replaced, the belt should always be inspected because if the compressor failed, the belt probably needs replacement too.
Major Brands for Original or Remanufactured A/C Compressor
The question always comes up whether to purchase a new Air Conditioning Compressor or a remanufactured Air Conditioning Compressor. Both new and remanufactured parts are available from most major companies, such as Bosch, A/C Delco, Denso, Delphi, Hitachi, Sanden, Four Seasons, Motor Craft, Valeo and all the major car manufacturers, such as Nissan, Toyota, Chrysler, Lexus, Infinity and General Motors. Companies such as ARC, A1 Cardone, Houston and National Compressor Exchange specialize in remanufacturing AC Compressors. During the remanufacturing process, the compressor is disassembled, all parts are inspected and parts that are good are often reused. This keeps the price down and is more environmentally friendly than simply discarding the whole unit. The outer case is almost always reused, as there is very little that will cause it to become a scrap item. In the rare case that it is scrap, it is often recycled by the remanufacturer. All remanufactured AC Compressors are tested before being boxed and shipped. So you can rest assured that a remanufactured Air Conditioning Compressor will last as long, or possibly longer, than the original.
Replacement of an A/C Compressor Requires Some Extra Skill
When replacing an AC Compressor, there are a few procedures that must be followed so the replacement Air Conditioning Compressor will give you years of trouble free service. First, the Freon needs to be properly captured to protect the environment. Even the newer R134a should not be released into the air. The system needs to be flushed, to remove any contamination, such as metal shavings. Any filters in the lines should be checked for contamination also. Before installing the new compressor, the system also needs to be flushed, this ensures there is nothing that will cause the new AC Compressor to fail. The correct type and amount of refrigerant oil also needs to be added. This is an important step that is often overlooked. Check for any labels on the replacement AC Compressor or in the repair manual. Always check all hoses for bubbles or cracking, as well as inspecting the metal lines for corrosion, kinks or wearing where they contact the vehicle. As stated earlier, the belt should also be inspected and likely needs to be replaced.
There are a few tools needed that you should be sure to have before starting. The correct size open end and box wrenches as well as a socket set, an air or electric vacuum pump to evacuate the system and an A/C flush kit. The whole job normally will not take more than 2 hours on most cars or light duty trucks.