A/C Problem

About 2 years ago my a/c compressor locked up so I had everything change out. Ok now for the problem ... Last year it started working only when it felt like it. Meaning I would get into the car and it would work fine and then the next time I would get in nothing but hot air. This went on for like 2 months and then finally nothing. No a/c. freon is good. Could this be a high pressure switch problem? I don't know much about the a/c system on my 95 Z-28. Is there a way to check to make sure the compressor is still good. Has any one else had any similar problem? Thanks for any help.

Try starting the car and turn the air on. Then remove the connector from the pressure switch and put a jumper across the pins of the connector. If the compressor then turns on you either have a bad low pressure switch or low freon. DO NOT leave the jumper on the connector, if the freon is low and you keep running it you'll burn it up. If the freon charge is good, you'll have to replace the low pressure switch, and this will require emptying the system, changing the switch, pulling the system down with a vacuum pump and recharging it.

See the problem with that is that it don't have a low pressure switch. It has a high pressure switch and I not sure if the same trick works on a high pressure switch.

All A/C systems have a low pressure switch, that is what protects the compressor from burning up.

First Question - Who changed out the compressor for you? Was it a professionally done job or a do-it-yourself thing?

If the system was not properly flushed out after a compressor failure you can have metal and debris clogging the orifice tube.
If the person who changed out the compressor did not flush the system & added the full amount of refrigerant oil for the system - then it is likely over charged with oil .
Also if the system was not properly evacuated to 800 microns or lower you can have excessive moisture in the system and the orifice tube can freeze up.
Or "D" all of the above
You can check the compressors performance & refrigerant charge with a set a gauges high side should be between 200psi and 250psi and the low side should be between 28psi and 34psi can be higher sometimes because R134 will run higher low side pressures (depending on how hot it is on the day you check) that is why 134 doesn't cool as well as R12. Ironically R134 will have less cooling capicity on the days you need it most because of the higher pressure traits of that refrigerant - the hotter the day the less the cooling capacity will be. (sad but true)

Side note - if you dont know what you are doing or how to interpret the guage readings you need to leave it alone and go to a qualified service professional.