It may sound like overkill, but the best thing to do with HOB filters is to buy a 2nd identical unit in case one dies so you can move your filter media and, in this case, biowheels, over to the new unit. It is very common for them to have trouble after being turned off. Even though everyone loves AquaClears, I had one not restart after a deep cleaning of my aquarium one time, and I didn't notice for about 20 minutes. I'm pretty sure the motor housing would have melted soon. Yes, I know I should have checked, but I am usually focused on making sure the canister is working and evaluating my landscaping. Comparing older filters with the motor in the Rena SmartFilter or the Eheim Liberty filters, you start to wonder if perhaps some refreshing might be in order.