A/C problems. Help!

For some time the A/C has been blowing air that is cool, but it doesn't seem to be as cold as it should be. Lately, it has only been blowing cooler air out of the passenger side vents. Then, I just drove somewhere and it is only blowing hot air. The smaller diameter a/c line under the hood still gets cold though. Please help. I live in south florida and it is as hot as Hades down here right now.

Thanks

probably just need to refill the coolant refrigerant.

Could someone please tell how to identify the low and high side valves on a 97 grand prix GTP.

Also, if someone could tell me how to diagnose the problem (1997 grand prix GTP) via checking the pressures (where the valves are for high/low sides and what the pressure readings should be for ambient temps in upper 80s/lower 90s)? Thanks. I really don't want to have to take it to a mechanic because you know you are getting screwed when you do that.

the low pressure port should be next to the refrigerant tank normally on the passenger side of the hood close to the fire wall. and no matter how hot or cold it is outside it should be i do believe between 25 and 35 psi cant remember off hand but if you get a gauge its in the blue area.

A/C system pressure does vary significantly due to ambient outside temps. Comparing readings between hi and low sides is the best way to insure there isn't a system blockage issue before attempting to just add refrigerant. I don't have the ambient temp pressure adjustment charts if front of me, but I believe I've seen a prior post that had them, so I'll see if I can do a search and find it for you.

The low side valve is near the firewall in the line between the accumulator (the metal canister looking item under the hood) and the evap core (the part inside the heater box). The hi side valve is in the line near the air cleaner assembly between the evap core and condenser (the part in front of the radiator). The hi side fitting is larger than the low side fitting, so the charge hose will not fit on it. This prevents a DIY from hooking into the wrong port and injuring themselves.

do they sell guage for high side? im getting good pressure on low side, wanna check high side to see if any blockage.