*CBHVAC* writes:

Although my tire patches back in
the 1970s worked fine on 300 psi R-12 high-side lines.

300PSI....on R12? Hummm....cant remember ever seeing a pressure that
high on a R12 system..

Right, high 100s to low 200s seemed typical gauge pressures. I was
thinking of the ratings printed on the hoses.