Sandin compressor locking up?

new radiator, new belts, now when I was checking the A/C, was running good. Compressor was running, then the clutch disengaged, when it engaged again, compressor was not turning, belts smoking. Shut motor down to check everything, looked good. Started it up, compressor turning just fine, kicked off, then back on and compressor not turning. Shut it down took the belt off, put a wrench on the compressor, and was hard to turn. Is this locking up or something else. This is on a Classic auto air system, been on the car for 10 years.