My electric oven is making a humming sound while there is no power running to it, I have switched it of from the mains and the electric plug on the wall.. But the humming is still there. This only started happening this morning, in the last week or so when I switch on the electric oven a loud grating sound is made.. I believe this to be the fan at the rear of the oven. It lasts for a minute or two then continues as normal. What really is now worrying me is the sound that it is making now as no power is running to it.. I've switched the electrical of though out the house, still humming, I've switched the water of ( just in case theres a leak somewhere as it sounds like a water pressure sound?) it's still humming, I've turned the gas of from the mains (just in case there's a gas leak) still humming.. I'm at a loss and really worried and I don't know what to do.. Does an electric oven have a back up power to make this noise? The noise has been from 8am this morning and still going strong now.. The noise seems to be coming from the bottom rear of the built in oven.. A humming sound, mixed in with a rattle snake sound.. Could it be an electrical short or something.. I'm lost.. Please help..?