My AC now rocks not sure why folks think it's marginal. I just got done fixing mine and it'll freeze you out of the car. The only way to diagnose for sure is to hook up some AC service gauges to it while the AC is running and check the readings. Without doing that to troubleshoot the system you are just shooting in the dark and flushing money away. The compressor is the most expensive part of the system if you trouble shoot it first it may point to a cheaper part.