94 Super Ranger 4 wheel drive

The light that lights when you push the button to enact the 4 wheel drive stopped lighting when my wife put the truck in 4 low, and I believe the 4 wheel drive isn’t engaged. The question I have is there a fuse for the electrics on this switch, and where is it? When my son in law had this truck he said the life went out and the 4 wheel drive didn’t work. He said that a friend of his replaced a fuse, and it was good to go.He of course doesn’t know what the guy did, and the guy who fixed it is deployed so I can’t ask him. Can anyone shed some light on this problem?