Repairing Car Air-conditioning (Part 2)


This part 2 series will describe how one could locate the Freon gas leakage. This is by far, the most common type of fault in car air-conditioning system.

Why Freon Gas Leaks?
Freon, in the process of compression and expansion, creates high pressure especially when it is operating under the hot sun. The pressure puts stresses on piping joints which are sealed by O-rings. These O-rings, made of rubber, can deteriorate with time and become deformed. Sometimes, the pressure could also cause hairline crack in pressure switches or the expansion valve. However, most Freon leakages are found in corroded tubing inside the evaporator because most of these tubing are made from filmsy aluminum materials for some reasons.

What Special Equipment Required?
Normally, one can detect the presence of Freon gas leakages without any special equipment although a gas detector would help.

What Else Do I Need to Know
Safety requirement. Read all about how to make the environment safe for one to inspect and repair the system.

1. Switch off the engine;
2. Locate the pipes and other air-conditioning components and pay particular attention to the location of piping joints and the weaker components with plastics such as pressure switches. Normally, these components are located in the engine compartment; only the evaporator and the expansion valve are located in the car compartment.

Next Step
1. Use the torch light, inspect every joint and component for evidence of oil leakage. Special oil used for lubrication of compressors are often carried away by Freon and gets circulated in the system during the operation. Oil will leak when there is Freon gas leakage. The trace of oily patches will often give the location of leak;

Problems in leak detection
There will be time when the simple surface inspection failed to locate the leak. This is because the leaks are sometimes located out of sight; for example, in the evaporator compartment or at the compressor.
For the leak at the compressor, one should be able to use the hands to “feel” the excessive oil from the bottom surface of the compressor. As for the evaporator, it will be hardly noticeable although there might be some minute traces of oil in the condensate pipings at times.
Sometimes, leaks are so minute and gradual that it leaves no trace of oil to tell the location of leak; then one would require the use of proper Freon detection instrument. In this case, a good charge of Freon is often necessary to detect the leak and the air-conditioning system will need to be in operation.

Gas Detection Instrument
There are basically 3 types or methods. The use of electronic instrument, the gas burner and the soap bubble method.
The electronic gas detector may cost around US$ 100-$ 200 and would require regular calibration and maintenance but it is safer to use. The electronic detector usually samples the air at a rate of about 1500 times per second and give an alarm if any halogenated refrigerants is detected. Sensitivity is around 0.1 oz/yr or 3 gr/yr.
The gas burner method is commonly used by mechanics in the older days and is still in use today.
The burner type is less sensitive and the detection is by observing the color of the flame. Normally, on detection of gas, the flame would turn bluish green for small leak and bluish violet for larger leaks.

Soap bubble method is one of the oldest and easiest method being used even today. It is a very rough method and less accurate and also, one would need to know roughly the location of the leak. It could be time consuming and works only on exposed components or piping joints.

Other Related Sites
1. Car Aircon Compressor Repairs
2. Car Air-conditioning Part 1
3. Car Air-conditioning Part 3
3. Car Freon Charging for Novice
5. Car Safety Inspection and Check at Home
6. Replace Engine Oil by Vacuum
7. Wheel Alignment Using Sideslip meter

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