Grid Filament Test
- Turn ignition switch to ON position. Press rear window defogger switch on. Rear window defogger indicator light should illuminate. Set DVOM to 0-15 volt range. Connect negative lead of DVOM to bus bar ground "B" terminal. Connect positive lead of DVOM to bus bar voltage feed "A" terminal. See Figure .
- DVOM reading should be 10-14 volts. A lower voltage reading indicates a poor ground connection. Touch negative lead of DVOM to a good body ground point. Voltage reading should not change. Connect negative lead of DVOM to bus bar ground "B" terminal and touch each grid line at midpoint "C" with positive lead. A reading of about 6 volts indicates line is good.
- A reading of zero volts indicates a break in line between midpoint "C" and bus bar voltage feed "A" terminal. A reading of 10-14 volts indicates a break in line between midpoint "C" and bus bar ground "B" terminal. Move probe toward bus bar voltage feed "A" or ground "B" terminal. Voltage will change when break is crossed. Repair grid line(s) as necessary. See GRID FILAMENT REPAIR under ON-VEHICLE SERVICE.