Compressor short cycles. I had the accumulator changed , the base was severely corroded by my mechanic about 2 years ago. Freon was recovered and freon was added. He got a new recovery machine so this work was done correct. The past month I have noticed the AC would blow cold, then not so cold. The gauge in the video is from the store bought freon cans, I kept the hose. When the psi gets above 50 the compressor clutch disengage, below 20 psi the clutch disengage. That would explain the loss...

2006 GT AC compressor short cycle