a friend of mine froze his tub over the winter and cracked a jet and some pipe,so he had a hot tub repair man come and fix the jet and the pipe but now when we turn the jet's on water comes threw the air knob? what could be the problem and how to fix?

Probably a loose jet, or inner jet fitting, and not at all related to the repair. Just tighten all jets. The venturi that creates a vacuum is created at the jet- if the eyeball, or inner jet fitting is loose, instead a creating a vacuum, it creates pressure, sending water out of the afc's. Very common. Either that, or it's possible (but very unlikely) that the repair guy crossed the air and water lines, but I doubt it.