Auto Air Conditioning & Heater Repair: 1966 Chevy P/U (C10) A/C PSI, r134 freon, 1966 chevy c10

Question
I have a 1966 Chevy C10 P/U with Factory Air that has been converted to using R134. What is the correct psi for this vehicle. On the compressor is says min is 140 psi low side. I am currently getting a reading of about 45 psi. Do I need to get to 140 psi.  

Answer
140 on the low side ?. Impossible.

When you convert a system from R-12 to R134. You install the recommended amount of R134 refrigerant oil and install ONLY 75% of the R134 freon into the system.


EXAMPLE ONLY. Your vehicles amount will be different.

Vehicle calls for 3.5 lbs of R-12 freon

You would install 75%  which is 2.62 lbs of R-134.


Are you using R-134 gages or R-12 gages.