Dang, i wish i had this info a few hours ago.

I put the gauge on the low side with the switch jumpered. It was about 85F out today. Static pressure was around 80 psi, and the AC was blowing cool. With the compressor engaged, engine at idle, it would stay at about 30psi. When holding the motor at around 3k rpm, the pressure would drop to about 10 psi.

I couldn't find an R12 pressure/temp chart like one uses for r134a. Anybody got one?? As the low pressure switch cuts out at 30 psi, i figure the system is low on charge. Thoughts???

I put a little more R12 in to the point where when at around 3k rpm, it is at around 15-20 psi. Plus, just for giggles i reconnected the low pressure switch. Now it works!

Without draining/evacuating the system, how can i tell what PSI my low side is supposed to be at given a specific ambient temp?