My a/c compressor was working perfectly one day and then stopped working overnight with no apparent symptoms or strange noises. It attempts to switch on and then stops. All the fuses, fans etc are working perfectly and the belt is new with good tension. When I "jump" the compressor by supplying 12V to the clutch (blue-green wire I believe) the a/c works perfectly again with no strange noises or symtoms, no bubbles in the sight glass etc. My diagnosis is a bad speed sensor...... Do you agree?? Is it dangerous to run the a/c as i have it rigged with the speed sensor & pressure sensors by-passed??