a/c pressures? 02 psd

[shadetreetx]

Yes, it is hot in Houston. My a/c will run cool and then all off a sudden get colder. Maybe a blend door issue? I have searched this forum and have not seen anyone post what the system pressures should be. I did see a post that the system needs 4.18 lbs but how do you check that without dumping & refilling? I have a DI 6 position chip with hi idle, 1100 rpm, which seems to help. Condenser is clean. Any help with psi vs rpm would be great. Thanks Bob