Manifold Gauges for R-134a Systems
Manifold gauges for 134-a systems work exactly the same was as R-12 gauges. But you can’t use the same set of gauges for both systems. They use completely different couplers and hoses. The gauge face on manifold gauges for R-134a systems have an identification plate that says “for R-134q use only” or something similar. And that’s exactly what is meant ! DO NOT try to use a set of R-134a gauges on a R-12 system. And don’t try to use a set of R-12 gauges on an R-134a system, either. The fittings are totally different, so each type of gauge is totally incompatible with the fittings and hoses used on the other system.