if you stick your finger inside the guard and push the impellar inward (before plugging in!), this has seemed to work for me whenever they won't turn.
Did they quit working after you unplugged them, or while they were plugged in/already running?
__________________
~Drew
10G Nano * 10G Sump * Deltec MCE 600 Skimmer * JBL Viper 150w MH * Zeovit * Vortech MP40W
Millions long for immortality who do not know what to do with themselves on a rainy Sunday afternoon. ~S. Ertz

|