I was doing a big water change and had shut off the filter (Emporer 350), and kept hearing this Whining. I unplugged the lights, still heard it. I unplugged the heater and it actually slowed to a stop like an engine winding down! I've never had anything like this happen before which is why I'll just toss it if nobody has an idea on a fix. It's well past the warranty, so I'd just replace it with one I'm not using right now.