OIL & O'RINGS:
Air Conditioning Compressor Oil is the lifeblood of the Air Conditioning system. There are different types of Air Conditioning Compressor Oil ranging from: PAG,ESTER, & Mineral (now rarely used).
When repairing or servicing your Automotive Air conditioning system be sure to check the quality of the oil. If major repairs are carried out it is advisable to flush the system and or components (where possible); removing oil in the system. It must then be charged with the correct oil and followed by a refrigerant charge.
An O-ring, also known as a packing, is a mechanical gasket in the shape of a torus; it is a loop of elastomer with a disc-shaped cross-section, designed to be seated in a groove and compressed during assembly between two or more parts, creating a seal at the interface. The O-ring may be used in static applications or in dynamic applications where there is relative motion between the parts and the O-ring.
O-rings are one of the most common seals used in Automotive Air Conditioning system design because they are inexpensive, easy to make, reliable, and have simple mounting requirements. They can seal tens of megapascals (thousands of psi) pressure.
These items should be inspected and replaced to ensure refrigerant is contained & Air Conditioning system is working to full potential.