Using the wrong A/C compressor oil is one of the most common causes of compressor failure. To maintain customer satisfaction, an in depth knowledge of oils and their composition is necessary.

 

The primary function of oil in the A/C system is to lubricate and control friction in the moving parts such as the compressor and TX valve. Oil also helps to maintain the integrity of seals and gaskets, lets heat escape from the compressor and controls corrosion.

 

The type of oil used in A/C compressors these days is a highly refined, non-foaming, low wax and low sulphur lubricant called PAG oil (polyalkylene glycol). These oils are specifically formulated for use in refrigeration and air conditioning systems and come in fit-for-purpose grades and viscosities.

 

Some manufacturers compressors have extremely tight tolerances, as little as 3um. Oil that is diluted, too thick, or the incorrect viscosity for the compressor will create more resistance and lead to system failure.

 

 

 

Ester Oil on the other hand is typically used in A/C systems that have been retrofitted to R134a. It is one viscosity only and performs well in high or low temperatures. Ester Oil is very stable and its chemical properties do not change when it comes in contact with chemicals found in retrofitted R12 systems.

 

It is important to ensure you’re using the correct oil type and quantity. Each compressor type is assigned a specific oil, often printed on the label of the compressor. Alternatively, you can check the oil application guide in the ‘Oils and Enhancers’ section of our latest catalogue to find the type of oil and quantity needed.

 

We recently shared the importance of regularly assessing and replacing the mighty drier, and it’s a similar story with oil in the A/C system. The drier will remove any solid impurities in the oil and will also capture moisture. When you’re changing the drier, it’s also wise to check the compressor oil - levels and purity.

 

PAG Oil is clear. Over time in a system and after extended running, oil will discolour. The chart below will help you be able to visually identify what’s happening with the oil and where possible faults could have occurred.

 

Amber (orange) or brown/black oil indicates a maintenance issue, and rules out any defects in materials or workmanship. When amber and brown oil are spotted, that is likely to void any warranty.

 

Grey oil indicates the compressor has failed due to a defect. Usually it will fail shortly after installation in this case, and therefore the oil hasn’t been in service long enough to become dirty or acidic.

 

Green oil indicates that dye has been used on the system at some point. Dye does not affect the performance of the oil and will allow for normal operation of the compressor.

 

Yellow oil indicates there is moisture in the system. As we repeatedly state, moisture is the enemy of refrigeration and allowing moisture to enter will also void any warranty.