First thing unplug it and pull it out (just in case it kicks on and wets you
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). Give a light shake and plug it in (does it vibrate? sit there like a rock?) if it comes on place it back in to the system. If it vibrates but not spin the impeller you have a blockage (so you'll have to do the following
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).
Most powerheads will allow you to take it apart. The thing to do first is unplug it. Then hold the top portion (the square-ish part) and look at the nozzle area to see a separation notch. Basically if you "twist" the top one way and the bottom another it comes apart at the notch with
"Very Little Force" (if you have to gorilla it you'll break it). Who's the maker? Hagen, Penguine, Maxi-Jet and few others separate this way. Now with the powerhead in two you'll see the impeller/mag-drive (some will have a rubber cap on the stem "DON"T LOSE THIS"). Now pull the cluster out, it should come up in one piece, if not that is why it's broke. Now if the cluster is intact then see if the stop notch on the plastic body of the impeller is there to stop at a certain point if not that is your problem. Both these issues can be fixed with epoxy (I'll explain how if this is the problem). If everything is peachie-keen see if there is grit or gunk in the hole the cluster came out of (the square-ish) the top. It should be slightly slimey but that's about it (old tooth brush and once over by the tap will do the trick
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). Put everything back together in sequence. Plug it in and it should work.
If not give a "light shake" to get it started.