These Low/High side retrofits/adapters/fittings will convert your old 3/8;; or 7/16;; R12
charging port and make it accept the R134a quick disconnect hose.
Fittings Have Removable Schrader Valves
1 Piece 19mm Blue Cap
1 Piece 22mm Red Cap
1 Piece Blue low side quick coupler
1 Piece Red high side quick coupler