Air-Conditioning Performance Testing

Performance testing provides a measure of A/C system operating efficiency. A manifold pressure gauge set is used to determine both high and low pressures in the refrigeration system. The desired pressure readings will vary according to temperature. Use temperature/pressure charts as a guide to determine the proper pressures. At the same time, a thermometer is used to determine air discharge temperature in the passenger compartment.

SERVICE VALVES
System service valves provide the attachment point for the manifold pressure gauge set. They are located in the low and high sides of most A/C systems. Two basic types of service valves were used on R-12 systems: stem and Schrader. R-134a systems have quick-connect fittings. The fittings for the gauges are connected to the system’s fittings. The gauge’s fitting has a knob that is turned in the clockwise direction to open the valve. No refrigerant should leak out when the gauge set is connected.

A thermometer is used to determine air discharge temperature in the passenger compartment.

Stem Valves. The stem valve was sometimes used on twocylinder reciprocating-piston compressors. The service valves are mounted on the compressor head. These valves can be used to

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Air-Conditioning Diagnosis: Noise and Odors on Your A/C system?

Often diagnosis of an A/C system can be done by observing the operation of the system, including listening for noises. When abnormal noises are heard, they can lead to the problem area.

A typical cabin air filter and housing.

NOISE
Often a customer’s concern is the noise emitted by the A/C system. The following discussion covers the common abnormal noises and their causes.

1. Clutch Noises. The clutch normally makes a clicking noise when it engages and disengages. This noise will become louder as the clutch wears. Once the clutch is severely worn, it will make a squealing noise when it is engaged. This noise can also result from oil on the clutch. A very loud screech or squeal can indicate a seized compressor. A bent drive pulley also can cause a growling or rubbing noise.
2. Hose Noise. The change in pressures in the suction/discharge hoses can set up vibrations that cause sounds to appear from the inside of the vehicle. The noise is typically caused by

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How to Convert (Retrofitting) R-12 Air Conditioning System to R-134a

The following guidelines should be followed when converting an older A/C system to R-134a. These guidelines should allow you to provide the customer with a cool vehicle and to meet current legislative mandates.

A label showing that an R-12 A/C system was converted to R-134a. This must be attached to the vehicle whenever the conversion has taken place.

The guidelines are listed in order and reflect the necessary steps for making this conversion.

1. Visually inspect all A/C and heater system components.
2. Use a refrigerant identifier to make sure the system only contains R-12.
3. Check the system for

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Automobile Air-conditioning: REFRIGERANT SAFETY PRECAUTIONS

Air-conditioning (A/C) service, in many ways, is different from service to other parts of the vehicle. Although there are few parts in the system, each component has a specific purpose and service procedure.

R-12 should be stored and sold in white containers, whereas R-134a should be stored in light blue containers.

That by itself is not a big deal. The challenge with the A/C is how it operates. The system operates on changes of refrigerant pressure. There are many things that can cause the pressure to change; some are part of the system, some are part of the environment, and some of them are faults or bad components in the system.

There are some precautions when you work with refrigerants.

1. Always work in a well-ventilated and clean area. Refrigerants are colorless and invisible. Refrigerant is heavier than oxygen and will displace it in a confined area. Avoid breathing the refrigerant vapors. Exposure to refrigerant may irritate your eyes, nose, and throat.
2. Refrigerant evaporates quickly when it is exposed to the atmosphere. It will

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Automobile Air-conditioning: Service Precautions

A/C systems are extremely sensitive to moisture and dirt. Therefore, clean working conditions are very important. The smallest particle of foreign matter in an A/C system contaminates the refrigerant, causing rust, ice, or damage to the compressor. For this reason, all replacement parts are sold in vacuum-sealed containers and should not be opened until they are ready to be installed in the system. If, for any reason, a part has been removed from its container for any length of time, the part must be completely flushed using only the recommended solvent to remove any dirt or moisture that might have accumulated during storage. If the system has been open for more than 2 minutes, the entire system must be completely evacuated and a new accumulator or desiccant bag must be installed.

A late-model air-conditioning system.

It is important to remember that just one drop of water added to the refrigerant will

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