Dolphin Dynamic quit working

Like many others my Dolphin Dynamic quit working summer before last. I let it sit all last summer and when I thought about buying a new one I decided to try the old one again. It worked perfect for three cleanings then it started doing the same thing it was doing two years ago. It will run for about 30 seconds and kick off. I did notice that the propeller quits turning a few seconds before the unit kicks off. Does anyone know what the cure is for this unit or should I just purchase a new one.