Contrary to popular belief, there is hope. First see if there is a current that goes to your grid. If there is, your defrost is NOT FUBAR. This only means that parts of your grid are corroded, hence not conducting the current efficiently or effectively. There is a paint on grid kit at the auto store that you can purchase if you want to retain the original grid look. All you have to do is use tape and mask between the grids. Paint it on and let it dry. This should remedy the problem.