Auto A/C Help on DVD
How the Auto Air Conditioning System Really Works
Now available on this 2 DVD set you will quickly understand all the principles behind how the automotive air conditioning system really works. Before you start to diagnose or repair any A/C system, you need to understand that the A/C system is really...

Auto A/C Terms - Glossary
Blower Fan
Every automotive A/C system cools the vehicle by removing the heat from the air entering the vehicle. Outside air enters the passenger compartment of the vehicle with the assistance of the blower fan. That fan is an...

Auto A/C Terms - Glossary
Boiling Point
Typically we think of boiling as hot. That is because when we think boiling, we are usually thinking about water. We know that water boils at 212F or 100C. Yes, that is hot. However, consider that other substances like refrigerant actually boil at temperatures below zero. As an example, R134a which is...

Auto A/C Terms - Glossary
Bowden Cable
Auto A/C and heater controls were typically connected from the dashboard control head to other components using a bowden cable. The bowden cable is a unique design because...

Auto A/C Terms - Glossary
British Thermal Unit - BTU
Understand that heat can be measured in a couple of different ways. If we use a thermometer, we are measuring the intensity of the heat. That is telling us how hot it is. On the other hand, if you want to know the quantity of heat, you would...

Auto A/C Terms - Glossary
Capillary Tube
Typically a part of thermostatic expansion valves or other A/C components that work by sensing temperatures of various other components of the A/C system, the capillary tube is typically a very small diameter tube that is filled with a gas and is made with a precisely calibrated length and inside diameter. That capillary tube is used to connect the...

Auto A/C Terms - Glossary
Celsius
A commonly used scale to measure temperature of the intensity of heat is the Celsius scale. The Celsius scale is also commonly referred to as teh Centigrade scale. In degrees Celsius, water will boil at...

Auto A/C Terms - Glossary
Change of State
Refrigerant in the A/C system can be either liquid or gas, often referred to as vapor. In fact, every A/C system has what is known as a liquid side and a vapor side. Also understand that the refrigerant in any auto A/C system continues to change from liquid to vapor and back to liquid, depending on where it is in the refrigerant circuit. When the refrigerant changes from liquid to vapor or from a vapor back to a liquid, that change is known as...

Auto A/C Terms - Glossary
Charge - Refrigerant Charge
Every A/C system is manufactured to hold a specific amount of refrigerant. The actual amount is always specified as a weight of refrigerant. That total weight or amount of refrigerant that the system holds it the Charge or Refrigerant Charge for that system. It is important to understand that...

Auto A/C Terms - Glossary
Charging Station
Any automotive A/C system can be serviced and recharged using manifold gauges, a vacuum pump and some method to measure or weigh the amount of refrigerant being charged into a system. Although this method is effective, more automated systems have been developed in order to save the service technicians time and provide a single work station to perform all functions. Known as charging stations, they will typically be made as...

Auto A/C Terms - Glossary
Clutch - Electromagnetic Compressor Clutch
Unlike commercial or residential A/C compressors where the motor is integral to the design, every automotive A/C compressor design is belt driven. With the use of a compressor clutch, the A/C compressor can be engaged and disengaged as required. The clutch assembly on automotive A/C compressor is typically referred to as an electro magnetic clutch. That is because...

Auto A/C Terms - Glossary
Clutch Cycling Switch
One of the most common auto A/C system designs is the cycling clutch configuration. Utilizing a cycling clutch means that the A/C system can provide proper cooling performance while not having to keep the compressor engaged all the time the A/C system is working. Instead of using valves to control the flow of refrigerant throughout the A/C system, the cycling clutch system turns the compressor on and off as required. Turning the compressor on and off is referred to as cycling and that is...

Auto A/C Terms - Glossary
Clutch Field - Clutch Coil
Every automotive A/C compressor clutch assembly is made up of three distinct components. The clutch hub or clutch plate is the front most component that will engage or click when the compressor engages. The pulley utilizes a bearing and is mounted on the front head of the compressor, turning with the belt attached. Behind the pulley...

Auto A/C Terms - Glossary
Clutch Pulley or Rotor
Every auto A/C compressor uses an electro magnetic clutch assembly to operate the compressor. That assembly includes a coil to create the magnetic field, a clutch plate attached to the main shaft of the compressor which will engage and disengage the compressor and a pulley or rotor...

Auto A/C Terms - Glossary
Cold
We all think about air conditioning as being cold or that it makes cold air. That really is not what happens. Air conditioning is really all about heat. That is because everything in our environment has some amount of heat in it. It is only when a substance reaches a temperature known as absolute zero that it no longer contains any heat. Therefore, you should understand that cold is not...

Auto A/C Terms - Glossary
Compound Gauge - Low Pressure Gauge
Every manifold pressure gauge set includes two color coded gauges. Typically, the high pressure gauge is read while the low pressure gauge is blue. High pressure gauges usually provide pressure readings up to four or five hundred psi, while low pressure gauges typically go to about 150 psi. The biggest difference in the low side gauge is that it is commonly called a compound gauge, because it not only shows pressure, but...

Auto A/C Terms - Glossary
Compressor - A/C Compressor
Considered to be the heart of the air conditioning system, the compressor pumps and circulates the refrigerant through the system. Replacing the A/C compressor is typically one of the most expensive auto A/C system repairs. For that reason, extra care should be taken to assure that it never runs out of lubrication. Understand that typically, the compressor is the only moving part in the system and is the only reason that the A/C system includes oil. The compressor is also a component that splits two different sides of the system. The A/C compressor suction...

Auto A/C Terms - Glossary
Compressor Cut Off Switch
The A/C compressor is a component that circulates and pumps refrigerant throughout the auto A/C system. It takes low side vapor refrigerant and compresses it to become high pressure, high temperature refrigerant that is discharged to the condenser. However, in cases where the A/C condenser can not properly cool that refrigerant and high side pressures begin to rise, the compressor cut off or cut out switch will...

Auto A/C Terms - Glossary
Compressor Shaft Seal
The auto A/C compressor includes several different seals. Typically, body seals are o-ring seals that prevent refrigerant from leaking externally. Internally, finely machined surfaces and gaskets seal the high pressure discharge side of the compressor from the low pressure suction side of the compressor. In all cases, those seals are static. They do not move. The only moving seal on the A/C compressor is the shaft seal. That is because the shaft seal must prevent refrigerant leaks while sealing on the main shaft of the compressor and...

Auto A/C Terms - Glossary
Condensation
When looking at the auto A/C system, condensation actually occurs in a couple of ways. Condensation is when a vapor or gas is cooled so that it changes state to become a liquid. In the A/C system, that occurs all the time in the condenser, because vapor refrigerant is being cooled. When that occurs, it changes state back to liquid. However, there is also condensation that occurs at the evaporator. The typical sign of a good working A/C system is when you see...

Auto A/C Terms - Glossary
Condenser
The condenser is one of two heat exchangers that is included on every A/C system. Typically mounted at the front of the vehicle, directly in front of the engine cooling radiator, the condenser has only one function in the auto A/C system. That is to...

Auto A/C Terms - Glossary
Contaminants in A/C Systems
Auto A/C systems can become contaminated quickly. That is usually a result of excess moisture that is in the system and can not be trapped or held by the drier. When that happens,....

Auto A/C Terms - Glossary
Control Head
Every auto A/C system provides controls in the passenger compartment. Those controls are typically mounted onto one assembly and that assembly is mounted on the dashboard of the vehicle. That entire assembly, which typically includes a temperature selector, mode selector, blower control switch and possibly a temperature knob or lever is considered...

Auto A/C Terms - Glossary
Corrosion in Auto A/C Systems
Corrosion in auto A/C systems is one of the leading causes of A/C systems failures. Corrosion, which is nothing more than the eating or wearing away of the A/C components in the system, is usually caused by the formation...

Auto A/C Terms - Glossary
Cycling Clutch Orifice Tube - CCOT A/C System
General Motors introduced the cycling clutch orifice tube A/C system in the 1977 model year. The unique advantage to having a cycling clutch with a fixed orifice tube was that...

Auto A/C Terms - Glossary
Cycling Clutch A/C System
On any auto A/C system, the compressor operates in order to pump and circulate the refrigerant. In order to reduce the use of the compressor and save resources like fuel, some A/C systems are designed to turn the compressor off when not required. Those A/C systems are referred to as...

Auto A/C Terms - Glossary
Dehumidify
Every automotive air conditioning system performs four basic functions to help improve passenger comfort and maintain temperature control. Besides cooling the air in the vehicle, the A/C system also...

Auto A/C Terms - Glossary
Desiccant
Automotive air conditioning system suffer problems when they get contaminated with moisture. That occurs over time as water droplets, at the molecular level, pass right through the membrane of the rubber hose. That water causes serious problems when mixed with refrigerants. That is why auto A/C systems require a...

Auto A/C Terms - Glossary
Dichlorodifluoromethane
The chemical substance (CC1 F ) used in earlier automotive air conditioning systems to absorb, carry and release heat. Dichlorodirluoromethane...

Auto A/C Terms - Glossary
Discharge A/C System
Whenever servicing auto A/C system or changing components, the A/C system has to have the refrigerant removed so that the system can be opened. Removing all or part of the refrigerant from the A/C system is commonly referred to as...

Auto A/C Terms - Glossary
Discharge Air
The A/C system is designed to remove the heat from the air that enters the vehicle. In doing that, it provides temperature control and passenger comfort. When diagnosing auto A/C systems, it is common to check the...

Auto A/C Terms - Glossary
Dicharge side
Every auto A/C system is divided into sides. There are the liquid and vapor sides of the system, and there are also the high and low sides of the system. The high side or high pressure side of the A/C system is commonly referred to ad the discharge side because...

Auto A/C Terms - Glossary
Drying agent
Unlike commercial A/C systems, auto A/C systems have to contend with moisture. That is because automotive A/C systems include flexible rubber hose sections that actually allows...

Auto A/C Terms - Glossary
Drier - Receiver Drier
Automotive A/C systems must have a means of trapping and holding moisture that may get into the system. One way of doing that is by using a receiver drier. The drier is usually...

Auto A/C Terms - Glossary
Equalizer Line - External Equalizer Tube
An equalizer line is typically part of come conventional thermostatic expansion valves or TXVs. The equalizer line should not be confused with the temperature sensing capillary tube. Very little refrigerant passes through the equalizer, even though the line will usually actually thread into the low side line of the A/C system at...

Auto A/C Terms - Glossary
Evacuate A/C system
Evacuating an A/C system is the process of pulling the A/C system into a vacuum. This is one of the most critical processes...

Auto A/C Terms - Glossary
Evaporator
Every air conditioning system includes two heat exchangers. That is because air conditioning is all about heat transfer. The evaporator is one of those heat exchangers. In order to remove the heat from the air entering the vehicle, the A/C evaporator ....

Auto A/C Terms - Glossary
Evaporator Equalized Valves in Receiver - EEVIR- VIR
A design change made on General Motors A/C systems in the early 1970s incorporated the expansion valve, suction valve and receiver drier into one unit known as a VIR assembly or Valves in Receiver. A slight design change to that was the...

Auto A/C Terms - Glossary
Evaporator Pressure Regulator Valve - EPR Valve
Early Chrysler Corporation A/C systems utilized EPR valves to maintain the proper refrigerant pressures in the evaporator. The ERP Valve was...

Auto A/C Terms - Glossary
Evaporator Temperature Regulator Valve - ETR Valve
Depending on the A/C system design, the evaporator pressure or temperature can be controlled in a variety of ways. On early model Chrysler Corporation A/C systems,...