If the 4x4 and Low buttons on a 1993 Ford Explorer stopped working could this be a fuse?

My 1993 Explorer buttons stopped working too. The Ford dealership told me that if you don't use the buttons occasionally like turning the 4x4 on and off while your car is warming up the brushes in the electric motor underneath the vehicle will stick. I got under the vehicle(not while it was running) and banged on it with a hammer it started working. But I now every once in a while turn those buttons on and off.