96 B2300 A/C problems

[Nolove]

My truck: 96 Mazda B2300 2.3L standard tran...I am having problems with my A/C. The A/C runs cold only if I have my foot on the gas. If I am at a complete stop the A/C will stop blowing cold air and the A/C clutch will start clicking on and off every 1-2 seconds and it makes my engine sound like its hesitating. I checked the pressure level of the freon and it was in the red section of the gauge that came with the refrigerant bottle. The temperature is hot where I live 90 degrees or more. I would like to know where I should start looking for the problem. No check engine light on... please help

 

[96b2300]

Are you checking the pressure while the ac clutch is engaged or while it is off?