I have a 93 ford taurus 3.8L V6 automatic GL. The A/C system was converted to R-134a in 2010. I just bought a A/C manifold gauge set and want to test my system. The instructions say to "read the pressure on both of the gauges and compare to the manufacturer's recommended readings." My question is where can I find the "manufacturer's recommended readings" for my car? I have looked under my car's hood and they are not their anymore. How can I get them?