found a can of r 12

[Theo]

93 Miata, never converted. Blows hot, has pressure in system. Previous owner said ac was blowing cold last year. How do you go about finding the leak before adding r 12. The in line to the condenser was a little loose. Tighten it, hoping this is it, but would like to know for sure. Would convert to 134, just never have heard anything good about drawing down system and adding 134 and it blowing cold enough without changing components.

[iscariot]

Generally - you hook up your gauges and suck down the system for a half hour, then close off your vacuum pump and hope the system holds vacuum for another half hour. If it holds vacuum you have a pretty good chance it'll hold pressure.

[Theo]

Do I just call around to find someone who is licensed to do r12?