mark79,80

I have an older set of R12 manifold gauges that I still use for corvettes
with R12. I would like to use this set for my newer cars that take R134. I have seen R134 couplers designed to thread into the R12
hoses.

Question: Is the scale on the R12 gauges the same as the R134 gauges in that pressure or vacume would seem the same regardless of
the gas? One set I saw in a catalog says it has R12 and R134 temperature scales. Is there then an advantage to purchasing another set of gauges desgned for R134?

Larry B.

I bought a R134a small can service set, cut the hose in half and spliced the two ends onto two R12 hoses. I works just fine and when you need the gages for r12 then splice the old ends back on. Vacuum and pressure are the same. Just service R134a to about 26 PSI on the low side. I used a vauum hose splice found on the "help" rack at A/Z or discount.

diablo kid

"Is there then an advantage to purchasing another set of gauges desgned for R134?"

No - not if you have a pressure temperature chart for the refrigerant you are servicing.
Having the pressure / temperature relationship printed on the gauges is convienient but not necessary.