One of our 3 speed fans suddenly only has one speed-slow. Any suggestions or comments to help us. It's HOT

Is it a remote fan?

Sounds like a bad capacitor. The capacitor is the black box inside the switch housing. Sometimes if it's gone bad it will look burnt or melted. You can replace it by wiring one of the same value(s) in it's place, but it will cost ~$10 plus shipping, unless you can get one free from Hampton Bay. And if you're going to go warranty, you're better off bringing the entire fan back to Home Depot for a replacement.