My A/C is blowing hot air

I have a 1997 Blazer. It's fully charged with the correct amount of pressure and oil as directed. The compressor kicks off and on when ever it wants, but even when it's kicked on I still have no cold air. Does any one have any suggestions? I'd greatly appreciate any. I'm in the south, and it's 101 today.

Did you check the AC system pressure?

How are you so sure the R134a is up to level?

Yes, the pressure is 45psi. Could it have something to do with my compressor kicking on and off whenever it feels like it?

Yes, the pressure is 45psi. Could it have something to do with my compressor kicking on and off whenever it feels like it?
I have a pressure/refrigerant gauge. It came with the kit from auto zone.

The compressor should run constant to get an accurate reading. Try adding a little refrigerant to get the compressor to stay on. The pressure will drop when the compressor starts running, then you just top it off to the proper level.

I have a pressure/refrigerant gauge. It came with the kit from auto zone.

Are you testing the pressure with the AC on MAX and on full cold with the fan on full blast?

I do have the A/C on max with the fan on high when checking the A/c. I'm afraid to add any more refrigerant. My gauge is already right on the line of too much refrigerant. That's why I'm confused over my compressor kicking on and off whenever it feels like it. I was always under the impression that when a compressor isn't working it doesn't come on at all. Could there be a wiring problem? I'm not familar with my car I've only had it for 2 months. Are there any relays or fuses under the hood I could be checking? Any help is greatly appreciated. thanks

I do have the A/C on max with the fan on high when checking the A/c. I'm afraid to add any more refrigerant. My gauge is already right on the line of too much refrigerant. That's why I'm confused over my compressor kicking on and off whenever it feels like it. I was always under the impression that when a compressor isn't working it doesn't come on at all. Could there be a wiring problem? I'm not familar with my car I've only had it for 2 months. Are there any relays or fuses under the hood I could be checking? Any help is greatly appreciated. thanks

Put the AC setting to Max and the fan on the highest setting. The compressor should run for a long period on this setting. Now check the suction accumulator and it should be very cold and sweaty. If you get this then the system is very close to the correct charge. If the compressor is cycling on and off you are low on charge so add untill the compressor runs. Be aware if you overcharge you may be pumping liquid around to the suction which will blow the compressor.

More than likely you are low on refrigerant.Your gauge may be saying it is full because the compressor isn't running long enough to bring the pressure down to the accurate level.

http://www.id-usa.com/how_to.asp

If you don't want to add more refrigerant to get the compressor to stay on.....pull the connector off the accumulator (the metal can) and jumper the wires together. The compressor will then stay on and you can make sure that you are getting an accurate reading.

If the pressure is okay and the system gets cold with the jumper wire, the pressure switch may be bad.

Thanks to everyone. My pressure switch was bad. I appreciate all the input.

sweet!