Preliminary Check

Turn ignition on. Turn defogger switch to ON position. If glass is not warm after a few minutes, check fuses. See WIRING DIAGRAMS  . If fuses are okay, check for battery voltage at grid feed wire. If battery voltage is present, check grid filament for good ground or breaks in grid wire filaments. See GRID FILAMENT TEST  under COMPONENT TESTS. Repair circuit(s) as necessary. If battery voltage is not present, check defogger switch, defogger relay and wiring harness.