Auto AC Compressor Problems

by Lee Sallings

Common air conditioning compressor problems include refrigerant leaks, electric clutch failures, and internal mechanical failures. Knowing the causes of these failures can go a long way to preventing them. But if you do have a compressor failure, knowing the damage caused by the failure is critical to a successful repair. Replacing the compressor alone may not solve the underlying cause of the failure, and may cause a premature failure of the new compressor.


Leaks in the air conditioning system are caused by faulty seal and hoses. Several seals in the compressor can fail. Normal heat cycling can cause the seals to fail. Heat cycling occurs when the system is heated during normal operation, and then allowed to cool while sitting. This constant heat cycling causes the seal to expand slightly and compress when hot, then contract slightly when cool. This back-and-forth expansion causes the rubber seal to rub on the metal parts, and the heat cycling itself hardens the rubber, causing a loss in sealing capability.The common symptom of this is loss of refrigerant over the cooler winter months, requiring a top-off of refrigerant at the beginning of warm weather. Another cause of seal failure is excessive pressure buildup. Pressure builds when the system is overheated, or the screen filter in the orifice tube is partially clogged. The common symptom is a system that cools initially, but becomes warmer as the vehicle is driven. This type of failure can be caused by an underlying condition that will not be cured with a seal replacement. The cause of the overheating problem, or the partially clogged orifice tube, must be addressed during seal replacement, or another failure will occur.


Electrically the compressor can fail at the clutch. The compressor clutch is an electromagnetic device that engages the compressor to the engine. This electromagnet can fail if the windings of wire in the coil become overheated and melt, or break. This causes the clutch to not engage when turned on. The most common cause of this failure is simple old age, but it can also be caused by an overheating engine. When the engine overheats, pressure in the system rises, and it becomes difficult for the compressor to operate. This puts stresses on the friction plate of the clutch and it begins to slip, causing heat buildup in the electromagnet.

Mechanical compressor failure.

Normal use will cause a mechanical failure over time. Just as in your car's engine friction causes wear on the parts, eventually they can't do their job anymore and the compressor fails. This wear can be greatly accelerated by an overheating engine. When the engine overheats, the condenser loses its ability to release heat just like the radiator does. This causes heat to build in the system, and pressures to rise. High system pressures cause the compressor to work harder to move the higher pressure refrigerant, and heat builds in the compressor as well. All of this leads to excessive wear, and particles of metal lost during this wear will clog the orifice tube and force the pressures even higher. Once the damage is there and the compressor fails, the orifice tube must be replaced along with the compressor to restore normal pressure.


About the Author

Lee Sallings is a freelance writer from Fort Worth, Texas. Specializing in website content and design for the automobile enthusiast, he also has many years of experience in the auto repair industry. He has written Web content for eHow, and designed the website. He began his writing career developing and teaching automotive technical training programs.