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Home >> Oldsmobile >> 1998 >> Cutlass Base >> Repair and Diagnosis >> Accessories & Equipment >> Heated Glass/Defoggers >> Rear Window Defogger >> Testing >> Defogger System Tests >> Rear Defogger Does Not Operate

Rear Defogger Does Not Operate

  1. Remove rear defogger relay from Underhood Bussed Electrical Center (U/H BEC), located in left side of engine compartment. Install a known-good relay from U/H BEC. Turn ignition switch to RUN position. Press rear defogger switch to ON position. If defogger grid warms, go to next step. If grid does not warm, go to step 3).
  2. Replace faulty rear defogger relay. Recheck system operation.
  3. Using a fused jumper wire, backprobe between U/H BEC 68-pin Brown connector C3 terminal D5 (White wire) and ground. Using test light, backprobe between U/H BEC connector C3 terminal C5 (Purple wire) and ground. If test light illuminates, go to next step. If test light does not illuminate, go to step 23).
  4. Using test light, backprobe between U/H BEC connector C3 terminal C5 (Purple wire) and ground. Press rear defogger switch ON. If test light illuminates, go to next step. If test light does not illuminate, go to step 14).
  5. Ensure defogger system is still on. Using test light, backprobe between LH Instrument Panel Bussed Electrical Center (LH I/P BEC) 30-pin Gray connector C2 terminal C1 (Purple wire) and ground. LHI/P BEC is located under left side of instrument panel. If test light illuminates, go to next step. If test light does not illuminate, go to step 7).
  6. Using test light, backprobe between LH I/P BEC 30-pin Black connector C3 terminal C12 (Black wire) and ground. If test light illuminates, go to step 8). If test light does not illuminate, go to step 9).
  7. Repair open in circuit No. 293 (Purple wire) between U/H BEC connector C3 and LH I/P BEC connector C2. Recheck system operation.
  8. Disconnect rear defogger grid connectors C1 and C2. Connect test light between rear defogger grid connector C1 terminal "A" (Black wire) and ground. If test light illuminates, go to step 10). If test light does not illuminate, go to step 11).
  9. Replace LH I/P BEC. Recheck system operation.
  10. Connect test light between rear defogger grid connector C1 terminal "A" (Black wire) and connector C2 terminal "A" (Black wire). If test light illuminates, go to step 12). If test light does not illuminate, go to step 13).
  11. Repair open in circuit No. 293 (Purple wire) between rear defogger grid connector C1 and LH I/P BEC connector C3. Recheck system operation.
  12. Repair open in rear defogger grid. See GRID FILAMENT REPAIR  under ON-VEHICLE SERVICE. Recheck system operation.
  13. Repair open in circuit No. 850 (Black wire) between rear defogger grid connector C2 and ground splice pack G402. Recheck system operation.
  14. Turn ignition switch to RUN position. Using test light, backprobe between U/H BEC connector C3 terminal A11 (Brown wire) and ground. If test light illuminates, go to next step. If test light does not illuminate, go to step 23).
  15. Using DVOM to check voltage, backprobe between U/H BEC connector C3 terminal D5 (White wire) and ground. If battery voltage exists, go to next step. If battery voltage does not exist, go to step 23).
  16. Disconnect A/C-heater control assembly 12-pin connector C2. Turn ignition switch to RUN position. Using DVOM, check voltage between A/C-heater control assembly 12-pin connector C2 terminal "C" (Brown wire) and ground. If battery voltage exists, go to next step. If battery voltage does not exist, go to step 18).
  17. Check voltage between A/C-heater control assembly connector C2 terminals "C" (Brown wire) and "K" (Black/White wire). If battery voltage exists, go to step 19). If battery voltage does not exist, go to step 20).
  18. Repair open in circuit No. 41 (Brown wire) between U/H BEC connector C3 and A/C-heater control assembly connector C2. Recheck system operation.
  19. Check voltage between A/C-heater control assembly connector C2 terminals "D" (White wire) and "K" (Black/White wire). If battery voltage exists, go to step 21). If battery voltage does not exist, go to step 22).
  20. Repair open in circuit No. 251 (Black/White wire) between A/C-heater control assembly connector C2 and ground splice pack G204. Recheck system operation.
  21. Replace A/C-heater control assembly. Recheck system operation.
  22. Repair open in circuit No. 193 (White wire) between U/H BEC connector C3 and A/C-heater control assembly connector C2. Recheck system operation.
  23. Replace U/H BEC. Recheck system operation.
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