I am not sure what is going on with my a/c. I had an issue where my compressor clutch would cycle every 10 to 15 seconds while driving, so much that my belt chirped when it switches on. I found a leak at the low side service port where the valve was not sealing. I evacuated the system, replaced the valve, pulled a vacuum, and filled it with 134a. The issue remains. At idle there is no cycling but when I rev the engine to 2000 or more the cycling begins. The clutch comes on at 40 psi on the low side and goes off at 200 on the high side. During idle the pressures stay constant at 24 on the low side and 170 at the high side. The air inside is cold reat at 28 to 30 degrees with an IR gun. I know this is not the right way to measure temp but its all I have at present. When I added 134a the clutch quick cycled but then went constant. The little tell tale gauge on the can of refrigerant was moving up and down until the compressor went constant and the needle was at the low end of the center blue scale and would not go any further up when more was added. Green is add more and red is too much. Like I said, I have no other idea what is wrong other than maybe the clutch air gap is too much and is why it is amplified now but otherwise working normally.

 

The chirp is probably coming from a clutch that's nearly worn out.