AC Pressure Numbers

[ddcrim]

My 74 F250 has been converted to R134A. I just checked the pressure readings and got
20 low side 250 high side at 1500 RPM, 85 degrees outside air, high humidity. All
of the AC parts were replaced last year and I really really flushed the system. Now
to the question. The factory shop manual says I'm at perfect levels, however an R134A
chart I have says I should be at 50/250. R134A is different than R12.
Who is right, and do I have a problem. ???????

[1972hiboy]

For an 85 degree day and 134a you should see higher low side pressure. however,,,,,r134a in r12 components acts a lil differently. If it were me i would tend to think the system was a little low and try adding some Freon but keeping an eye on the high side. Hopefully an a/c guy will chime in if im way off base.