Grid Filament Test
- Start engine. Turn defogger on (press and release rear defogger switch button once). Using grounded test light, lightly touch each grid line. If test light shows full brilliance at both ends of all grid lines, check for loose ground wire. Test light brilliance should gradually change as test light probe is moved from left to right side of grid.
- Contact each grid line a few inches on either side of glass center line to eliminate possibility of missing a break in grid line. If a problem on a grid line is detected, place test light probe on grid line at power bus bar and move probe toward ground bus bar until light goes out, indicating a break in grid line continuity. See Fig 1
. If break exists in grid line, go to GRID FILAMENT REPAIR
under ON-VEHICLE SERVICE.
Courtesy of GENERAL MOTORS CORP.