Car A/C R-134a Systems

By 4 April 2015

Systems using R-134a are similar in appearance and function to system using R-12. Although they use physically larger, heavier-duty compressors, condensers and evaporators, cycling clutch, orifice tubes, pressure switches, receiver-driers, etc. – are virtually identical to the parts used on R-12 systems. But they’re not interchangeable! Installing a component designed for an R-12 system in a system built to use R-134 a – or vice-versa may cause component failure and could damage the system.

If you’re working on a 1992 or newer vehicle, always determine whether is uses R-12 or R-134a before servicing or troubleshooting it. How so you know whether the system in your vehicle uses R-12 or R-134a? Look for special identification decals or labels on the major components. For instance, some 1992 and later Ford Taurus models with a 3.OL engine use an R-134a system. Ford distinguishes these models with a special yellow tag that says “R-134a NON-CFC” on it. These models also have a gold colored compressor, and green colored O-rings are used throughout the system. Other manufacturers use similar means of identifying R-134a systems.

What else should you look for? The high-side and low-side service fittings on an R-134a system are completely different from those used on an R-12 system. On an R-12 system, the high-side service fitting is a 318-inch 24 for screw-on couplers; the low-side fitting is a 7116-inch 20 (also known as a 114-inch flare fitting). On an R-134a system, the high-side and low-side service fittings are special 1M-inch Acme-type fittings with no external threads. They have internal threads but they’re for the specially-designed caps unique to R-134a systems; the low-side service valve uses a special quick-release service coupler that’s also unique to R-134a systems. And the valve cores on both fittings are also unique to the R-134a systems. In other words, there’s no possibility of confusing these fittings with those used on earlier R-12 systems.

In 1991, Saab introduced a 1992 model as the first vehicle to use an air conditioning system designed for R-134a. In 1992, Chrysler, Ford, GM, Infiniti, Mercedes, Nissan, Saab and Volvo debuted models using R-134a. By 1993, most vehicles were equipped with R-134a systems.