Trouble Shooting

Verify customer complaint by operating rear window defogger system. Check for blown fuse(s), loose or corroded connectors, or damaged wiring harness. Check grid filament for operation and condition. See GRID FILAMENT TEST  under COMPONENT TESTS. If problem is found, repair or replace components as necessary. If fuse(s) are blown, inspect for shorted power distribution circuits. See POWER DISTRIBUTION in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Check ground circuits for open or high resistance. See GROUND DISTRIBUTION in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Check control switch operation. Replace relay with known-good relay.