1990 Chevy Lumina No cold air thru vents

Due to the charts in this diagnostic, I will need to email the info as a PDF, Check your email.

My a/c compressor seems to be operating ok, I can hear it come on. But only get hot air no matter where temp control is adjusted to. Even when on vent it blows hot air, it is like I have no temp control. I did not see on the e mail you sent where the diagnostics talk about that or do I just not understand. It seems very complicated.

Start the a/c, when the compressor start up, count the seconds until it shuts off, and tell me how hot is it when you do the test.

After starting a/c, the compressor stays on until I turn off a/c. Ran a/c for 5 mins.The air never changes from hot to cold. One of the lines off the compressor is cold and is sweating, both cooling fans cycle on and off like normal, only can't get cold air, blows hot air only. When selector is on vent it still blows hot air like temp selector is on hot.

What is the weather? Unless you are in the 80's and 90's the compressor should cycle itself on and off. But at this point we need a good reading of the system with a manifold gauge set, this will tell us if the system has a blockage, of if the problem is in the inside of the car, either a control, or stuck temp door inside the A/C plenum.

The temp outside was in the mid 70's. Don't know what you mean by system check with manifold gauge set. Are you talking vacuum? Where is the temp door inside the plenum? Something that I can check.

Manifold gauges are attached to the high and low side service ports, the system is run for a few minutes , then readings are taken of the gauges. IF the system were blocked, and that is likely, the gauges would tell us by the readings... Temp in the mid 70's, the compressor SHOULD be cycling on and off every 90 seconds or so. If not cycling, something is wrong.
Check your email I sent a diagnostic chart...