I've done the exact same thing to several heater boxes and a/c boxes with excellent results. The repairs are almost never seen from the outside.Mustangerbob1 said:Go to Autozone, et al, and buy the small fiberglass repair kit that has some fiberglass mat in it. Take it apart, rough sand the back of the crack, lay some mat and catalysed jel, and let it set up. The gel should fill the crack from the inside. Touch up any that overflows the crack, and good as new. Good time to rebuild the unit.