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Everything has a certain amount of heat except at absolute zero ( -460 degrees.F ). An ice cube May feel cool to the touch, but actually it just has less heat than your hand. That means heat is transferring from your hand to the ice cube. This is the principle behind how an A/C cools the air in a car. Heated air is forced across a cold evaporator and is transferred to the refrigerant gas, making the air less hot. The refrigerant carries the heat away from the evaporator to the compressor. The refrigerant is super heated by compression and is forced through the condenser where cooler outside air takes the heat from the refrigerant. Its next stop is the expansion device (TXV or CCOT) which meters refrigerant into the evaporator and we start over again. SIMPLE ISN'T IT! WHAT DOES A DRIER DO- DRY? IT'S NOT THE FREON!! It's the oil in the refrigerant that absorbs moisture and holds debris in the system. Replacing the drier / accumulator, in addition to evacuation, will assure better performance.

Why Replace the Receiver-Drier?

The receiver-drier must be changed each time a system is empty regardless of the reason for loss of refrigerant. It should also be changed every three years, because the desiccant pellets will break down and clog the expansion valve. This will in turn cause the system to become inoperable and May damage the compressor.

The receiver-drier is strictly a disposable item and is thought of in the same terms as a fuel, oil, or air filter. In fact, if any component fails or is replaced for any reason, the receiver-drier must also be replaced to prevent corrosion and moisture in the system. The receiver-drier performs three functions:

-It filters the system of non-condensables.

-It receives the liquid refrigerant and maintains a certain level of liquid at the bottom at all times in a properly charged system.

-It contains a stack of pellets called desiccant (drying agent) to trap and absorb moisture. NOTE that moisture is the most harmful enemy of the air conditioning system. If any moisture is in the system, it will combine with the refrigerant to form hydrochloric acid which is extremely corrosive to metal components.

Replacing the receiver-drier is essential when servicing the A/C system. Whenever you replace a component of the A/C system you must also replace the receiver-drier. If you do not change the receiver-drier there could be serious damage to the other parts of the system, which could be very costly. WHY INSIST ON FLUSHING
There is no way to know how much oil is in a system
(1) Flushing eliminates excess oil from previous services. You do not want to add another full charge of oil when replacing a compressor and adding oil to the system.
(2) Sludge and debris, left in the system, clogs the orifice tube/expansion valve and can damage the valves in a compressor. Accumulator
Accumulator is canister after the Evaporator. Freon expands dramatically when it is heated up as it passes through the evaporator in the passenger compartment, absorbing the heat and changed into gas. The accumulator receives the (R12 or R134a) in the gas state as it leaves the passenger compartment evaporator. It has desiccant to trap moisture.

Alignment - Belt

The engine belts that drive the A/C compressor must be in alignment. A reason for them to be out of alignment is that the pulleys on the A/C compressor do not match with the engine pulleys. This can be due to improper installation of engine pulleys or A/C clutches as well as incorrect brackets used in mounting the A/C compressor.

Charge, Re-Charge

This describes installing (R12 or R134a) into the A/C system. Usually charging a system means installing the proper amount of (R12 or R134a) into the system that it needs. Re-charging suggests that only a portion of the freon has been lost from the system and is being replaced. Recharging a system that leaks can delay repairs, and could be illegal in some states. If a system has lost all of its (R12 or R134a), recharging is never advisable until you find the cause of the leak and the leak is repaired. Open systems could have contamination of air and moisture that enters the system after the (R12 or R134a) pressure is lost.


The compressor receives the Freon in a gas-like state and compresses it into liquid and circulates it into the condenser where the heat is taken out of the (R12 or R134a). The compressor is lubricated with special oil. It is very important to use the correct oil to the compressor and system. Some seals and gaskets May not work with some oils.


The condenser converts (R12 or R134a) from the gas-state back to the liquid state. The condenser is a radiator-like unit made up of coils. It is often mounted in front of the car radiator. (R12 or R134a) comes into the condenser from the A/C


A/C systems can be contaminated with metal particles from the normal wear of the compressor and tiny amounts of water moisture. Contamination can cause a system to fail. Protection against contamination is provided by the filter screen on the Expansion Tube and the desiccant in the bottom of the dryer or accumulator. Other forms of contamination May be the wrong kind of oil, wrong kind of liquid charge or other material that will interfere with the cooling system. Almost 100% of moisture is normally removed from the system when it is evacuated prior to installing (R12 or R134a).


Drier is used before the evaporator and after the condenser. The Filter Drier is where the system will filter out small amounts of contamination and moisture from the system. Each time the system is opened or worked on the Drier should be replaced. The desiccant inside the dryer will absorb moisture. Also spelled drier. Evaporator
Evaporator is a small radiator like unit that is stationed inside the car, usually near the heater core. The Evaporator receives liquid (R12 or R134a) into its coils. The fan inside the car circulates hot air over the evaporator coils and (R12 or R134a) absorbs the heat and is converted to gas which then flows to the accumulator. The cooled air flows into the car.


In the installation or repair of your A/C you should be sure to use a vacuum pump to draw a vacuum on the entire system. Vacuum is usually measured at 29 inches. We recommend holding the vacuum for 2-4 hours without fluctuation (most industry sources suggest 30 minutes). The vacuum will extract any moisture from the system as well as provide some assurance against possible leaks.

Expansion Valve, Expansion Tube

Also called the orifice tube. This component often has a mesh screen and is found in the evaporator inlet pipe (liquid line). In some cases this item is found in the outlet of the condenser. Its purpose is to limit the flow of the high pressure liquid (R12 or R134a) and thereby meter the flow of refrigerant to the evaporator as a lower pressure liquid. The screen serves the purpose of trapping metal particles that break loose from the compressor or other components. Expansion Valve come in two types, Block and Right Angle. The block valve is located at the evaporator and its purpose is to constantly check the temperature of the (R12 or R134a) and allow the proper amount of (R12 or R134a) to enter the evaporator. The right angle valve comes in two types (internal equalized and external equalized). This valve is also found before the evaporator and its purpose is to control the amount of (R12 or R134a) going into the evaporator.

Fittings - Hose

A/C hoses are designed to control liquid and gas at high pressures and temperatures. The hoses are usually flexible and terminated with special metal fittings at the ends that prevent leaks and provide a sure seal and connection between components. If you see blisters or bumps on the hoses you have a leak. You have to replace the whole line because today we use hoses that have a liner.


During installation or repair of A/C systems, the system should be flushed with clean special purpose fluids prior to the Evacuation and charge with new (R12 or R134a). This process is critical to the success of the job and long life of the system. Flushing removes contamination such as particles of rubber or metal that could be harmful to the system.

R12 and R134A

R12 Freon has been used since the 60's in automotive A/C systems. Government regulations and increasing prices have made R12 to high of liquid to use today. R134a is the newer version of R12 with out the harmful effects to the atmosphere. R134a is a much smaller and more efficient than R12. R134a typically runs a higher head pressure and tends to leak out quicker from high side leaks than R12. R134a requires the that the best components are used in your ac system. In some cases you will need to replace your condenser and evaporator to a higher efficient model so that R134a can perform properly. Warning. Do not mix R12 with R134a. Make sure you use the proper Oil.

Leak Test

A/C systems sometimes develop small leaks just like car tires do. When a leak develops the A/C (R12 or R134a) can be lost over the course of a few minutes or a day or two. One form of leak testing is done by charging a system with dye. When the dye escapes, it leaves a colored deposit at the point of the leak. Another form of leak testing is done by a simple pressure test, however this kind of test rarely helps locate the point of a leak. Another is done with a electronic leak tester.

Oil PAG or Ester

Oil is designed to work with (R12 or R134a). Its primary purpose is internal lubrication for the compressor. A small portion of oil circulates through the system. Some systems collect the oil at the bottom of the accumulator and return the oil directly to the compressor through a separate line. It is very important to use the correct oil with the correct (R12 or R134a)

Pressure Switch

The pressure switch senses internal pressures and can cycle the compressor off and back on based on minimum and maximum pressure limits. Pressure switches also turn on or off you condenser fan or Radiator Fan.

Pressure Relief Valve

Relieves pressure from the system to protect components when internal pressures become too high.

Schrader Valve

This is the same kind of valve you have on your car tires and bicycle tires. It is used at one or two places in A/C systems to provide an access point to measure pressures and to remove or install (charge) (R12 or R134a) into the system.
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