Glossary — Aircondition.com Knowledge Base

accumulator

Accumulators are used on systems that accommodate an orifice tube to meter refrigerants into the evaporator. It is connected directly to the evaporator outlet and stores excess liquid refrigerant. Introduction of liquid refrigerant into a compressor can do serious damage. The chief role of the accumulator is to isolate the compressor from any damaging liquid refrigerant. Accumulators, like receiver-driers, also remove debris and moisture from a system.

compressor

The compressor is the pump that's responsible for compressing and transferring refrigerant gas through the air conditioning system.

condenser

This is the area in which heat dissipation occurs. The condenser, in many cases, will have much the same appearance as the radiator in you car as the two have very similar functions. It's location is usually in front of the radiator. As hot compressed refrigerant gasses are introduced into 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.

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desiccant

Desiccant is the material used to trap moisture in an air conditioning system. Desiccant is placed in the accumulator or receiver-drier during the manufacturing process. There are several different desiccant materials are in use. Some desiccants are not compatible with R-134a. The desiccant type is usually identified on a sticker that is affixed to the receiver-drier or accumulator. Newer accumulators and driers use desiccant type XH-7 and are compatible with both R-12 and R-134a refrigerants.

evaporator

The evaporator is the component that absorbs heat from the passenger compartment. Refrigerant enters the bottom of the evaporator as a boiling low pressure liquid, and exits the top of the evaporator as a low pressure vapor. The evaporator provides several functions. Its primary duty is to remove heat from the inside of your vehicle. A secondary benefit is dehumidification. As warmer air travels through the aluminum fins of the cooler evaporator coil, the moisture contained in the air condenses on its surface. Dust and pollen passing through stick to its wet surfaces and drain off to the outside.

FOT

Acronym for Fixed Orifice Tube.

The fixed orifice tube, or FOT, is used to meter refrigerant. It's located in the inlet tube of the evaporator, or in the liquid line, somewhere between the outlet of the condenser and the inlet of the evaporator. Most orifice tubes in use today 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. The filter screen is used to prevent the small orifice from becoming clogged with debris. Orifice tube coloris used to indicate orifice size.

H block

A simplified thermal expansion valve is Chrysler's "H block" design. This type of expansion valve is located at the evaporator, between the evaporator inlet and outlet tubes and the liquid and suction lines. Usually found underhood, exposed near the center of the firewall. Joe Petty would tell us that many ambulances and big trucks use em' too!

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miscible

The chemistry term miscible refers to the property of various liquids that allows them to be mixed together. By contrast, substances are said to be immiscible if they cannot be mixed together, e.g., oil and water. Miscible. (n.d.). Wikipedia. Retrieved April 23, 2006, from Answers.com Web site: http://www.answers.com/topic/miscible

orifice tube

The fixed orifice tube, or FOT, is used to meter refrigerant. It's located in the inlet tube of the evaporator, or in the liquid line, somewhere between the outlet of the condenser and the inlet of the evaporator. Most orifice tubes in use today 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. The filter screen is used to prevent the small orifice from becoming clogged with debris. Orifice tube coloris used to indicate orifice size.

PAG

Stands for Polyalkylene glycol. It is made from synthetic base stock and is OEM recommended for use in automotive A/C systems which use refrigerant R-134a.

receiver-drier

The receiver-drier is used on the high side of systems that use a thermal expansion valve. This type of metering valve requires liquid refrigerant. To ensure that the valve gets liquid refrigerant, a receiver is used. The primary function of the receiver-drier is to separate gas and liquid. The secondary purpose is to remove moisture and filter out dirt. The receiver-drier sometimes has a sight glass in the top.

sight glass

Before the advent of R134a, the sight glass was often used to determine system charge. Under normal operating conditions, vapor bubbles should not be visible in the sight glass. The use of the sight glass to charge the system is not recommended in R-134a systems, as cloudiness and oil that has separated from the refrigerant can be mistaken for bubbles.

SUS

"Saybolt Viscosity Seconds" A method used to determine oil viscosity using a viscometer. Read more about oil in the Engine Oil Bible

thermal expansion valve

The thermal expansion valve, or TXV is used separate the high and low pressure side of the refrigerant system. Mainly used on import and aftermarket systems. The expansion valve can sense both temperature and pressure, and is very efficient at regulating refrigerant flow to the evaporator. Several variations of this valve are commonly found. Another example of a thermal expansion valve is Chrysler's "H block" type.

transducer

Found on the high pressure side of many late model vehicles. Transducers provide pressure input to the computer. Transducers look like a typical high pressure switch, but, this type of switch will have more than two wires. You'll find a ground wire, a low voltage (5 volts) reference wire, and a return wire. The computer will interpret low return voltage as low pressure. At the other end, the computer will interpret high voltage as high pressure. Compare actual pressure against scan data value to determine if transducer is reading correctly.

TXV

Acronym for Thermal Expansion Valve. The thermal expansion valve, or TXV is used separate the high and low pressure side of the refrigerant system. Mainly used on import and aftermarket systems. The expansion valve can sense both temperature and pressure, and is very efficient at regulating refrigerant flow to the evaporator. Several variations of this valve are commonly found. Another example of a thermal expansion valve is Chrysler's "H block" type.