The rear defroster on a Toyota Corolla, also called the defogger, is made up of several lines across the rear windshield. Voltage travels through these lines, also called "elements," to remove the frost from the window and aid rear visibility. A break in one of these elements will disrupt the circuit and cause the element to not work, reducing the whole defroster's effectiveness. You can repair a small break in this system on your Corolla without removing the windshiled or any other difficult task.
Buff the surface where the damaged defroster element is using light strokes with a piece of fine steel wool. Clean off the area afterward with rubbing alcohol.2
Place horizontal strips of masking tape along the borders of the damaged element in the exact location of the damaged spot. The tape should be lined up with the outer edges of the element.3
Add vertical strips of the tape so they tape and close off the element just outside the damaged spot. There should be about 3/4 inch of space on each side outside the damage zone.4
Mix up the epoxy material from a specialty repair kit available at many auto parts stores. Follow the kit's specific instructions for this.5
Brush and apply the epoxy material to the damaged area using the kit's included brush.6
Wair 24 hours for the repair epoxy to cure before starting up the rear defrost in the car.