Thursday, January 19, 2017 Detailed Auto Topics
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When an air conditioner suffers a failure, proper repair will be expensive. An improper fix will be vastly more expensive. Diagnosis, cleanliness and a full repair are the keys to a long-lasting air conditioner.

Other than leaks, compressor failure is the most common breakdown in an automotive air conditioner system. This is unfortunate, as many compressor deaths may have been avoided with simple steps.

Replacing a worn belt is an easy way to head off compressor problems

worn out belts are checked with a gauge rather than a visual inspection

Modern EPDM belts do not always crack or show wear like older neoprene belts did. A worn belt can slip, creating a huge amount of heat and a compressor clutch failure. Checking the belt, with a proper gauge and replacing when needed can prevent this problem.

Cleaning a condenser to keep air conditioner pressure under control

All heat removed by the air conditioner is given off at the condenser. A proper flow of air is necessary to keep internal pressures at safe levels. Electric fans and fan clutches wear out and can cause catastrophic failure very quickly. The previous article covers this in detail. Dirt, bugs and debris can also plug the fins of a condenser and prevent proper air flow. The external fins of a condenser can be cleaned with detergent, formulated for the purpose, and a flow of water, from a hose.

Gently spray water through the condenser to clean

The best job is done by reverse washing, after removing the radiator. If this is not practical, washing from the front is far superior to not cleaning the condenser.  Care must to taken that the spray does not damage the fins, and water spray should not reach the engine.  Cleaning the condenser and testing air flow every couple of years, can prevent many air conditioner problems.

Keep the evaporator core clean to prevent compressor failure

A plugged cabin filter can cause compressor failure

Clogged cabin air filters can restrict air flow through the evaporator. This may result in refrigerant that does not flash fully to a gaseous state. Liquid refrigerant is captured by the accumulator, but with insufficient air flow, there may be an overflow. Any liquid refrigerant that reaches the compressor will soon cause damage.

Vehicles without a cabin or those that have not been replaced can suffer from plugged fins in the evaporator. This will keep air from circulating and may cause compressor damage. Such cores can sometimes be cleaned without removal. Access to the evaporator may also be impossible without the dash being taken out. Keep the cabin filter and the interior of the vehicle clean can help prevent this expensive repair.

Air conditioner compressors do not just die; they are killed

Reasons why air conditioner compressors fail

When an automotive compressor fails, finding and correcting the cause is imperative. Replacing a compressor without correcting the cause of failure will result in repeat failure and a much higher level of contamination in the system. When a compressor dies, a large amount of metal and debris are released. Failure to remove this hazard completely, will result in a repeat failure.

Conditions for proper air conditioner repair must be near sterile

An air conditioner system should be approached with a near sterile attitude. Any debris that enters the system will cause major problems. A quick look into the service area of a repair shop will tell a lot. A dirty environment is no place for air conditioner repair.

Avoiding compressor failure is best, by replacing a unit with any problem, before failure. Noise, low pressure or any sign of restriction of the system is an early warning. Replacing a damaged compressor, before it fails, is far less expensive and more certain than trying to clean a contaminated system.

A plugged orifice is a symptom of a larger problem

When a compressor is damaged, from liquid ingestion, high pressure, over-charge or other reasons, metal is generated. This metal comes from the internal parts of the compressors. The oil and refrigerant will transport these contaminants throughout the system.

A plugged orifice tube is a symptom of a larger problem

Debris leaving the compressor first begins to accumulate in the condenser. Modern air conditioner condensers have extremely small passages, and the tubes are very long. Larger particles begin plugging these tubes. Smaller particles flow deeper into the condenser until they lodge. Others pass through contaminating the orifice tube. Any metal that passes through the orifice screen returns to the compressor and does additional damage.  A plugged orifice tube will restrict oil flow, further adding to the problem.

condenser passanges are very tiny and cannot be cleaned

When compressor failure causes contamination, the condenser will also need to be replaced. There is no method to clean these tiny passageways. Any debris that remains will eventually work its way through and start the failure cycle again. The best method is to prevent compressor failure, or address the problem before contamination occurs.

A severely contaminated system, after four compressor failures

The contents of the line above consist of burned oil and metal. This line was taken from a system, in which the compressor had been replaced four times within two years. At this stage, replacement of the entire system is often the only remedy.

Cleaning contaminated air conditioner systems

Cleaners in a can or a flushing gun are better than nothing, but are usually ineffective in removing contamination. They pose another problem of leaving the cleaner behind. Cleaners left in air conditioner lines may dilute the lubrication, cause a breakdown of desiccants in the accumulator and create failures within the system.

A profession liquid refrigerant flushing machine

Professional machines cost several thousand dollars and use liquid refrigerant for cleaning the system. These machines, pulse and reverse flow to remove debris in components. The compressor is removed, and the machine is attached to the hoses. After thoroughly flushing, the liquid refrigerant is extracted, cleaned and recycled.

Even machines like this are not able to clean condensers or expansion valves. They do a great job on hoses, lines and evaporators, but other components still need to be replaced.

Threads do NOT seal AC lines and tightening will not help

When air conditioner components are replaced, all O-rings must be replaced, with the correct size and material.  Refrigerant O-rings come in a multitude of sizes and different materials.  Using the wrong seal will result in a leak.  Most air conditioner fittings are made of aluminum and are not sealed by the threads.  Tightening a leaking connection will not help and will gall their threads, ruining both parts.  A clean connection, with a new O-ring requires a minimum of torque on the fittings.  Over-tightening will cause these fittings to strip when they are removed for a proper repair and greatly increase the cost.

Diagnosing and correcting the cause of failure, combined with thorough cleaning and replacement of all contaminated parts will give a long-lasting job. With air conditioner repair, the cheapest way out is usually the most expensive way in.

Please also see:

Part one, electrical problems with air conditioners 

Part two, understanding refrigerant gauges

Part three, finding and repairing air conditioner leaks

 

 





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