Wednesday, November 22, 2017 Detailed Auto Topics
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Air conditioner leaks are one of the most common failures. Proper repair can be expensive, but will only need to be done once. Improper repair will cost many times more and cannot sometimes be fixed.

The first segment of this series covers electrical system problems and diagnosis. Part-two shows how to check the refrigerant system with gauges. In this article, finding and repairing leaks is the topic.

Finding refrigerant leaks

When an automotive air conditioner is low on refrigerant, there is a leak from the system. Leaks are far more critical today than in the past. Older systems contained a large quantity of refrigerant, some as much as five pounds. Modern systems hold much less, often as little as nine ounces. Losing only three ounces in such a system represents 30% of the charge and the system may quit working. Charging is also far more critical. Adding 12 ounces of refrigerant can destroy the system.

Professionals use many different methods to find leaks

oily residue indicates a refrigerant leak

The simplest method is a close inspection. Refrigerant contains oil and when it leaks, there is often a residue that can be seen. Oily traces on a hose, especially near the connections is a sign of a leak.

Oily residue indicates a refrigerant leak

This condenser shows a problem, by the large wet spot, cause by oil leakage. Condensers are very soft aluminum and are often damaged by road debris and contact with other objects. Acid from a leaking battery will also damage a condenser, eating the thin metal away. Large leaks on external components can be found with just an inspection.

Soapy liquids, designed to bubble, make the job easier. Special leak detecting products can be brushed over suspected areas and will show bubbles if a leak is present. These products do a good job, for a very low-cost and can be safely used by the home enthusiast to find problems.

A leaking a/c line with dye and a special light

Much smaller leaks are easier to find when fluorescent dye is added to the system. Dye is often present in new vehicles and can be added to others as a diagnostic procedure. This chemical is colorless to the eye, until viewed using a special light and glasses. Under the light, a greenish-yellow color makes leaks easy to see. This can save much time when searching for slow leaks.

Evaporator cores are a common point of leakage. These cannot be readily inspected, as they are usually hidden by the dash of the vehicle. Finding very small and hidden leaks is done with electronic leak detectors.

Some leak detector types

Electronic detectors use many technologies to find refrigerant leaks. These devises can be expensive, costing hundreds of dollars. With hidden leaks, the probe of the detector can be used to check areas that cannot be seen. For even smaller leaks, a more recognizable refrigerant may be added, and nitrogen used to raise pressure. This method can often find leaks undetectable with other methods.

Beware of refrigerant containing sealer

Some part stores, and many internet companies sell a refrigerant mixed with other things. Sealer may be the worst additive. A leaking system will not be repaired by sealer and may be made extremely expensive to repair. Inadvertently adding contaminants to an air conditioner prevents a professional from recycling the refrigerant.

A refrigerant identifier in use

Federal law advises refrigerants, removed from an air conditioner, must be recycled or disposed of properly. Recycle machines are very expensive and easily damaged. Before servicing an air conditioner, a refrigerant identifier is used to determine if the contents of the system are contaminated.

air conditioner contaminated by sealer in refrigerant

Improper blends of refrigerants and sealers will show as contaminated when tested. When this occurs, very expensive removal and disposal procedures have to be followed. The debased contents cannot be recycled, and it is illegal to release it into the atmosphere. Adding substandard refrigerant to an air conditioner may cost the vehicle far more than they expect, for removal and disposal. The costs of this procedure can be shocking and many shops may simply refuse to work on the system.

Repairing air conditioner leaks

Tightening a connection will only make the leak worse

Air conditioner lines are sealed by O-rings. The external threaded fittings are NOT a seal and only serve to hold the parts together. Tightening the fitting may destroy the threads and usually make the problem worse. Most lines and fitting on air conditioners are aluminum and very soft. Tightening the fitting will gall the threads and destroy both components.

When a leak is found, the system needs to be evacuated to remove the refrigerant. The connection can then be disassembled, and the O-rings replaced. The new O-rings should be coated with refrigeration oil and reassemble, tightening only enough to hold the connection.

Hoses leak because they are beginning to deteriorate or they are cut. Repair involves replacement of the hose. Clamping a leaking hose may crush it and introduce rubber debris into the system. Particles from a damaged hose can clog the valve or orifice and cause a much larger repair.

a leaking evaporator core with dye in the system

Leaking evaporators and condensers will also have to be replaced. With thermal expansion and the pressure involved, no material will effectively seal a condenser or evaporator. Replacement is the only repair that will work. Any oil that is contained in the parts replaced should be measured, so it can be replaced when the unit is recharged.

Once the leaking component is replaced, a vacuum pump is used to remove air and moisture from the system. The lowered pressure will cause moisture trapped within the system to boil so it can be drawn out. Proper evacuation of a system takes hours and should not be rushed.

After repair and evacuation, any oil removed is replaced and the proper weight of refrigerant is returned to the system. A properly repaired and charged system will cool well and last for years. In the final article of this series, prevention of problems and replacement of the compressor is covered.

Please also see:

Part one, electrical problems with air conditioners

Part two, understanding refrigerant gauges

Part four, preventing and repairing compressor failure





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