AC driving me crazy

[sdj539]

Hello, new member here. I have a 2002 pathfinder sec4x4 with 3.5 and a/t and 230k miles. I've been trying to diagnose an ac problem. The ac would be cold and work fine and then other times it will only blow hot air. I hooked up manifold gauges and I was getting high low pressure side #s (120 psi) and low high pressure # (under 90 psi). I suspected a possible clog. I evacuated and pulled vacum and refilled with as close to exact .99lb r134a as possible using scales. It then worked fine for a day then back to intermittent warm then cold. Usually if it was cold it would stay cold for the day even with starting and stopping the car running. When I pulled the vacum I held it for 1 hour and it dropped .5" mercury. I figured that could have been connection of manifold gauges. When the air was blowing hot the suction line was hot. So I again assumed clog. I replaced the condenser and expansion valve. Bingo, great very cold air. Now 2 days later I'm back to high low side pressure and low high side pressure. Static pressure with car off for 1 hour are 90/90 with ambient temperature of 80.

Any help would be greatly appreciated. Thank you 

[Slartibartfast]

My best guess is that whatever clogged your old expansion valve, also clogged the new one, but I'm not an aircon guy. There should be some troubleshooting in the service manual (free download from Nicoclub, should be the HA section), might point you in the right direction?