Which color O'Ring should you use when servicing your a/c system? Colors are usually the manufacturer’s choice. Often the vehicle manufacturers subcontract parts of the a/c system out. The subcontracted section of the a/c system may use one color for the o'ring while the rest of the a/c system may use another color. What is more important to consider is the material that the o'rings are made from. In R134a systems, o'rings are usually made from HNBR (Hydrogenated Nitrile Butadiene Rubber) and are usually green in color. HNBR is the best type of o'ring because it can withstand all of the heat and temperature ranges that today’s automotive a/c systems produce. There are other materials that can be used for o'rings that will work in the lower temperature areas of the automotive a/c system, but to be sure, it is always safer to use HNBR o'rings. Paying a few pennies more for HNBR o'rings are pennies well spent when you compare it to the cost of having to replace your refrigerant often.
