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turned On, a distinct voltmeter needle deflection 2. Turn the ignition switch to the On position. Depress the rear window defogger switch to the On 3. Using a 12-volt DC voltmeter, contact the rear glass heating grid terminal A (right side) with the The above checks will confirm rear window defog- ger system operation. Illumination of the rear win- If the rear window defogger system does not oper- ate, the problem should be isolated in the following (1) Confirm that the ignition switch is in the On position. (2) Ensure that the rear glass heating grid feed and ground terminals are connected to the glass. (3) Check the fused B(+) fuse in the Power Distri- bution Center (PDC). The fuse must be tight in its receptacles and all electrical connections must be When the above steps have been completed and the rear glass heating grid is still inoperative, one or • Rear window defogger switch • Rear window defogger relay • Body Control Module (BCM) • Rear window grid lines (all grid lines would have to be broken or one of the feed wires discon- When the above steps have been completed and the heated mirror glass heating grid is still inoperative, • Body Control Module (BCM) • Programmable Communications Interface (PCI) data bus • Driver Door Module (DDM) or Passenger Door Module (PDM) • Outside rear view mirror heating grids. duces a severe voltmeter deflection, check for a short REAR GLASS HEATING GRID For complete circuit diagrams, refer to Rear Win- dow Defogger in the Contents of Group 8W - Wir- grid lines, the following procedure is required: (1) Turn the ignition switch to the On position. Turn the rear window defogger system on. The rear (2) Using a 12-volt DC voltmeter, contact the rear glass heating grid vertical bus bar on the right side (3) With the positive voltmeter lead still contacting the rear glass heating grid vertical bus bar on the (4) Connect the negative lead of the voltmeter to the right side bus bar and touch each grid line at Fig. 1 Rear Window Glass Grid Test 1 – TERMINAL “A” 8N - 4 ELECTRICALLY HEATED SYSTEMS WJ DIAGNOSIS AND TESTING (Continued) |