I think that's a good possibility doitmyself - I thought the same thing myself. I thought the best approach would be to get a tachometer and measure the motor RPM and compare that to the rpm stated on the tag (if it has one). If it's reading slower by a significant margin that's your answer. For the shop vac that's a good idea - maybe cap the inlet outside and put the shop vac hose to pull a vacuum. For the ice this has been happening pretty consistently and with the warm winter it's been above freezing for most of the time.