Grid Filament Test
- Turn ignition and rear window defogger on. Using a DVOM, check for voltage between defogger positive wire terminal and body ground. See Fig 1. If voltage exists, go to next step. If voltage does not exist, check for faulty defogger relay, faulty defogger switch, or an open Black/Green wire on Accord and Odyssey. On CR-V, check for an open in Black/Brown, White/Green, Blue/Yellow or Black wire. On Prelude, check for faulty defogger coil, ICU, or an open in Black/Green wire. Repair as necessary.
- Using a DVOM, check for continuity between defogger negative wire terminal and body ground. If continuity exists, go to next step. If continuity does not exist, check for open in defogger ground wire.
- Connect DVOM positive lead to center of each defogger grid wire. Connect DVOM negative lead to defogger negative wire terminal. See Fig 1. If reading is about 6 volts, defogger grid wire is okay. If reading is greater than 6 volts, an open exists between center of defogger grid wire and negative side. If reading is less than 6 volts, an open exists between center of defogger grid wire and positive side. To locate break, move probe along grid wire until meter needle moves abruptly.
Courtesy of AMERICAN HONDA MOTOR CO., INC.