After hitting 118 degrees in Phoenix the other day, I decided to check my a/c pressure levels to ensure it is operating at its best. I'm having some problems interpreting the results. Engine warmed up, recirc on, high fan speed, 1500 rpm: 90 ambient temperature the low side was 24 psi and the high side was 295 psi 110 ambient temperature the low side was 33 psi and the high side was 335 psi The FSM says at 86-95 degrees the low side should be between 22 and 36psi. So my pressure is probably on the low side, but in range. The FSM says the high side should be between 199 and 228psi, so my pressure is high (even after adjusting for above averge tremperature). In both cases the site glass showed a whitish foam. The FSM has a troubleshooting guide, but it does not indicate a condition where low side is okay, but high side is high. Could I have air trapped in the system? Incidentally, my A/C is working fine. It blows cold air and can keep up with 100+ degree temperatures, but I am trying to maximize performance for those really sweltering days. Thanks for any advice.