Can I use the same gauge set for R12 and R134a?

[Michael L.]

Guys,

have to charge my AC system on a couple of vehicles. Can I use the same gauge set for both R12 and R 134a or will there be a problem with cross contamination?

Mike

[Rocco S.]

Re: Can I use the same gauge set for R12 and R134a?

Michael,

Theoretically you can use the same manifold gauge for both R-12 and 134a. The system operating pressures are similar--but not the same. I don't think cross contamination would be a problem. The issue is the fittings. R-12 fittings use a threated flare fitting and 134a fittings are of quick-disconnect type. So unless they make adaptors you will not be able to connect the manifold gauge hoses.
If successful using adaptors, you will need to read only the pressure scale. So you will need to know the correct low and high side limits.

[Harry S.]

Re: Can I use the same gauge set for R12 and R134a?

Rocco is correct about differences in fittings. The fittings did not need to be different for R12 or R134. The reason they are different is to avoid a service mechanic trying to put the incorrect Freon into the system. The change was just to avoid human error.

[Tom L.]

Re: Can I use the same gauge set for R12 and R134a?

Standard refrigeration or A/C fittings are 1/4" flare consistently accross the industry. Period. There are 2 exceptions, 1- some mini split a/c systems use a 5/16" fitting. I have no idea why but it annoys the hell ot of me. But this is unrelated to your question. 2- When 134a became the go to refrigerant in cars, the industry wanted to prevent automotive a/c mechanics from mixing refrigerants. To be fair that wasn't a bad idea. Automotive a/c guys never had to differentiate one refrigerant from another. It was new territory for them. Us commercial refrigeration types have been dealing with this forever.

So... you don't say what year your car is. If it's an old R12 system then 1/4 flare type guages will work, if a 134 system then they won't work. You may or not have noticed that there are (usually) 3 inner circles of numbers. they are pressure temperature charts added to make our lives easier. And in my world they do. Here's why.

Keep in mind that as long as you can connect your "pressure" guage to a system you can recored pressure. Regaurdless of the refrigerant pressure is all you need. If knowing what the pressure/temperature relatonship for a given refrigerant means then you just need a Pressure/temperature chat for the refrigerant you're using. Not a new guage set. P/T charts are easily accessible through google.

Did this help? Who knows. But I tried : )