Air Conditioning problem
1985 Isuzu Truck 4 cyl Two Wheel Drive Automatic 90000 miles

I have tried to start my a/c but it feels and sounds like the clutch in the compressor is not kicking in. I have tried putting freon in it but it will not bubble in the sight glass when injecting. The front of the compressor will not trun at all. i have put ester oil in it but it still will not turn. Should I keep trying to put freon in it or should I just put up the cash for a whole new compressor