I had a leak that was repaired a few months ago and the system was recharged. Now I am having trouble getting the clutch to engage. It has worked before and after the leak fix (even just a couple of days ago) but it's inconsistent when it works. I tried jumping the A/C clutch relay, fuse, high pressure switch, and low pressure switch. All give the same result; I hear the engine de-rev a touch and hear another small hiss sound and then the motor goes back to normal idle speed and nothing else. Where to do from here?