Here's a comparison of R-134a to R-12 refrigerant vapor pressures at specific temperatures.
R-134A has a slightly lower pressure at evaporator temperatures (30-40 degrees), but R-134a also has a much higher pressure at condenser temperatures (120-150 degrees).
NOTE: For best heat transfer, condenser temperatures should be 30-40 degrees hotter than the ambient air temperature entering the condenser.
[img]http://farm3.static.flickr.com/2549/3992604130_60c40f2a32_o.jpg[/img]
(edited) Put picture below of the chart. It disappeared here ? IDK why, Tom