If it's that rubbery coating that helps you grip it, probably over time has deteriorated into some other chemical and can't be fixed. I'd look for a non functional but clean one and swap the guts out. I threw two away (customers trash) today, sorry. I've seen this happen on several of the models but can't figure out if it is due to bad production runs or environmental. Heat? Sun? The steering wheel on my old jeep did it too.