Air Conditioning Terms
ACCUMULATOR
Accumulators are used on systems that use an orifice tube to meter refrigerants into the evaporator. The accumulator is connected directly to the evaporator outlet and stores excess liquid refrigerant. The primary function of the accumulator is to isolate the compressor from any damaging liquid refrigerant. Like receiver driers, accumulators remove debris and moisture from the air conditioning system.Moisture is the prime enemy to your air conditioning system. When moisture mixes with refrigerant it forms a corrosive acid which will destroy your compressor.
COMPRESSOR
The compressor is a belt driven pump that is fastened to the engine and usually referred to as the heart of the system. The pump is fastened to the engine and is responsible for compressing and transferring refrigerant gas.
The air conditioning system is split into two sides: a high pressure side and a low pressure side, otherwise defined as discharge and suction. Since the compressor is a pump, it must have an intake side(suction) and a discharge side. The suction side (intake) takes in the refrigerant gas from the outlet of the evaporator. In some air conditioning systems, the refrigernat gas is drawn in via the accumulator.
The refrigerant gas is then compressed and sent to the condenser, where it then transfesr the heat that is absorbed from the inside of the vehicle.
CONDENSER
The condenser's function is to radiate heat. It is very similiar looking to the radiator in your car and is usually located in the front of the radiator. Condensers must have good air flow whenever the system is in operation. Rear wheel drive vehicles rely on the existing engine's cooling fan while on front wheel drive vehicles, the condenser air flow is supplemented with one or more electric cooling fans.
When the hot compressed gases flow to the top of the condenser, they are cooled off. As the gas cools, it condenses and exits the bottom of the condenser as a high pressure liquid.
CONTAMINATION
Air conditioning systems can be contaminated with metal particles from the normal wear of the compressor and tiny amounts of water moisture. Other forms of contamination can be the wrong kind of oil, liquid charge or other material that will interfere with the cooling system. 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.
EVACUATE
If you are installing an air conditioing system or doing a repair, you must use a vacuum punmp to draw a vacuum on the entire system. Vacuum is usually measure at 29 inches. Most industry sources suggest a minimum of 30 minutes. The purpose of the vacuum is to extract any moisture from the system as well as provide assurance against possible leaks.
EVAPORATOR
The evaporator serves as the heat absorption component. This small radiator like unit usually near the heater core inside the car provides several key functions: remove heat from the inside of your car and dehumidification. When the warmer air travels between the aluminum fins of the cool evaporator coil, the mositure contained in the air condenses on its surface. Dust and pollen passing through stick to the coils wet surface and drains off to the outside. When the weather is humid, you will see water dripping from the bottom of your vehicle which is normal.
The ideal temperature of the evaporator is 32 degrees fahrenheit or 0 degrees celsius. Refrigerant (R12 or R143a) enters at the bottom of the evaporator as a low pressure liquid. The warm air passing through the evaporator fins causes the refrigerant to boil. As the refrigerant begins to boil, it can absorb large amounts of heat. This heat is then carried off with the refrigerant to the outside of the vehicle.To keep the evaporator operating at its ideal temperature, temperature and pressure regulating devices must be employed.There are several variations of devices used, but their main function of keeping the pressure in the evaporator low and keeping the evaporator from freezing is the same.
EXPANSION VALVE (ORIFICE TUBE)
There are many variations of pressure regulators used today to control the refrigerant pressure and flow into the evaporator. The two most common types are the orifice tube and thermal expansion valve.
The thermal expansion valve is usually found on import and aftermarket systems. This type of valve can sense both temperature and pressure and is very efficient at regulating refrigerant flow to the evaporator. This component often has a mesh screen and is found in the evaporator inlet pipe. In some cases, it is found in the outlet of the condenser. These valves can become clogged with debris and have small moving parts that may stick and malfunction due to corrosion.
The orifice tube is probably the most commonly used pressure regulating device. It is used widely on GM and Ford models. It is located in the inlet tube of the evaporator somewhere between the outlet of the condenser and the inlet of the evaporator. Most orifice tubes measure approximately three inches in length and consist of a small brass tube surrounded by plastic and covered with a filter screen at each end. Unfortunately, it is easy for these tubes to become clogged with small debris.
FITTINGS - HOSES
Air conditioning 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 to prevent leaks and provide a sure sal and connection between components. If you see blisters or bumps on the hoses, there is a leak and the hose must be replaced.
FLUSH
During installation or repair of air conditioning systems, the system should be flushed with clean special purpose fluides prior to the evacuation and charge with new R12 or R134a. This process is crutial 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.
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 your condenser fan or radiator fan.
PRESSURE RELIEF VALVE
The pressure reflief valve relieves pressure from the system to protect components when internal pressures become too high.
R12 / R134A FREON
R12 freon has been used in automotive air conditioing systems since the 1960's. Due to government regualtions and increasing prices, R12 has become to expensive and harmful to the environment to use any longer. The more efficent R134a is the new version of R12. R134a typically runs a higher head pressure and tends to leak out quicker from high side leaks than R12. In order for R134a to perform properly, you may need to replace your condenser and evaporator to a higher efficient model. Never mix R12 with R134a and make sure you use the correct oil for the refrigerant you are using.
RECEIVER DRIER
The receiver drier is used on the high side of systems that use a thermal expansion valve. Since the expansion valve requires liquid refrigerant, a receiver drier is used to ensure the expansion valve gets the liquied refrigerant. The primary function of the receiver drier is to separate liquid and gas. The secondary purpose is to remove moisture and filter out debris.
SCHRADER VALVE
Same type of valve found on your car tires and bicycle tires. It is used in air conditioning systems to provide an access point to measure pressures and to remove or install R12 or R134a into the system.
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