It's a v8, right? My compressor was also leaking from the same seal, but worse than yours - even then the ac went a year between recharges...but i eventually replaced the compressor to have a permanent fix. If you put a 9v battery across the clutch you can see if the clutch engages (and air con goes cold)...if that works then you can work your way through the wiring to understand why the 12v signal is not getting to the clutch.