When we get those in (they come in here all the time) the usual problem is....
Ok, so maybe we hardly ever get them in here, but try standing outside while they are on and help them through a full sweep. If you can feel the motor trying to work but its just too weak, you need a motor. If it has no motor power at all, it may still be a motor that's shorted and its popping a circut breaker.
Other than that, I'm outa here. We're closing early.