Hey,


You can pickup a cheap set of gauges online or even Harbor freight. The R134a cheapos are universal with "adaptor fittings" for the ends. Don't like that they have 2 valves instead of 3. Nice to blow any oil from the high side hose back through...
Site glass is your best tool without gauges. Also temp of the low side line- Got a IR thermometer? You can measure the temp on each line and it will be close(yea I know it will be off a bit for super heat).

look at a pressure/temp chart www.ackits.com/aacf/ptchart.cfm should get you there. @ 105F, coil temp should be 29F and high pressure 240-290psi. 110F, coil @ 32 PSi.
Now compare it to R134a: 110F, coil temp of 65F !!!! yea... that's why R-12 kicks butt in hot weather.

Michael