INSPECTION PROCEDURE 7: Defroster Function does not Operate.: Diagnosis

Required Special Tools: 

1. MB991223: Test Harness Set

1. STEP 1. Check the A/C and outside / inside air changeover damper control motor operation. 

   Q: Do the A/C and outside / inside air changeover damper control motor work normally? 

   1. YES:  Go to Step 2.
   2. NO:  Refer to "INSPECTION PROCEDURE 9  ."
2. STEP 2. Measure the voltage at defogger connector F-16. 
   1. Disconnect defogger connector F-16, and measure the voltage at the junction block side.
      Fig 1: Disconnecting Defogger Connector F-16

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   2. Ignition switch: ON
   3. Defogger switch: ON
   4. Measure the voltage between terminal 1 and ground.
      • The measured value should be approximately 12 volts (battery positive voltage).
   Fig 2: Measuring Voltage Between Terminal 1 & Ground

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   Q: Does the measured voltage correspond with this range? 

   1. YES:  Go to  Step 14.
   2. NO:  Go to Step 3.
3. STEP 3. Check the defogger relay continuity. 

   Follow the table below to check the defogger relay for continuity.

   Fig 3: Defogger Relay Continuity Chart

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   Fig 4: Checking Defogger Relay For Continuity

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   Q: Is the Defogger relay continuity in good condition? 

   1. YES:  Go to Step 4.
   2. NO:  Replace the defogger relay. The defogger system should work normally.
4. STEP 4. Measure the voltage at defogger relay connector C-215. 
   1. Disconnect defogger relay connector C-215, and measure the voltage at the junction block side.
      Fig 5: Disconnecting Defogger Relay Connector C-215

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   2. Measure the voltage between terminal 5 and ground.
      • The measured value should be approximately 12 volts (battery positive voltage).
   Fig 6: Measuring Voltage Between Terminal 5 & Ground

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   Q: Does the measured voltage correspond with this range? 

   1. YES:  Go to  Step 7.
   2. NO:  Go to Step 5.
5. STEP 5. Check defogger relay connector C-215 for damage. 
   Fig 7: Checking Defogger Relay Connector C-215

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   Q: Is defogger relay connector C-215 in good condition? 

   1. YES:  Go to Step 6.
   2. NO:  Repair or replace the connector. The defogger system should work normally.
6. STEP 6. Check the wiring harness between defogger relay connector C-215 (terminal 5) and the battery. 
   NOTE: Also check junction block connector C-212 and intermediate connector C-126. If junction block connector C-212 and intermediate connector C-126 is damaged, repair or replace the connector .
   Fig 8: Checking Wiring Harness Between Defogger Relay Connector C-215 & Junction Block Connector C-212

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   Fig 9: Checking Intermediate Connector C-126

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   Q: Is the wiring harness between defogger relay connector C-215 (terminal 5) and the battery in good condition? 

   1. YES:  Check that the defogger system works normally.
   2. NO:  Repair the wiring harness. Check that the defogger system works normally.
7. STEP 7. Measure the voltage at defogger relay connector C-215. 
   1. Disconnect defogger relay connector C-215, and measure the voltage at the junction block side.
      Fig 10: Disconnecting Defogger Relay Connector C-215

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   2. Ignition switch: ON
   3. Measure the voltage between terminal 1 and ground.
      • The measured value should be approximately 12 volts (battery positive voltage).
   Fig 11: Measuring Voltage Between Terminal 1 & Ground

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   Q: Does the measured voltage correspond with this range? 

   1. YES:  Go to  Step 10.
   2. NO:  Go to Step 8.
8. STEP 8. Check defogger relay connector C-215 for damage. 
   Fig 12: Checking Defogger Relay Connector C-215

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   Q: Is defogger relay connector C-215 in good condition? 

   1. YES:  Go to Step 9.
   2. NO:  Repair or replace the connector. Check that the defogger system works normally.
9. STEP 9. Check the wiring harness between defogger relay connector C-215 (terminal 1) and ignition switch. 
   NOTE: Also check junction block connector C-211. If junction block connector C-211 is damaged, repair or replace the connector .
   Fig 13: Checking Wiring Harness Defogger Relay Connector C-215 & Junction Block C-211

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   Q: Is the wiring harness between defogger relay connector C-215 (terminal 1) and ignition switch in good condition? 

   1. YES:  Check that the defogger system works normally.
   2. NO:  Repair the wiring harness. Check that the defogger system works normally.
10. STEP 10. Check defogger relay connector C-215 and defogger connector F-16 for damage. 
    Fig 14: Checking Defogger Relay Connector C-215

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    Fig 15: Checking Defogger Connector F-16

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    Q: Are defogger relay connector C-215 and defogger connector F-16 in good condition? 

    1. YES:  Go to Step 11.
    2. NO:  Repair or replace the connector. Check that the defogger system works normally.
11. STEP 11. Check the wiring harness between defogger relay connector C-215 (terminal 4) and defogger connector F-16 (terminal 1). 
    NOTE: Also check junction block connector C-217. If junction block connector C-217 is damaged, repair or replace the connector .
    Fig 16: Checking Wiring Harness Defogger Relay Connector C-215 & Junction Block Connector C-217

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    Fig 17: Checking Defogger Connector F-16

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    Q: Is the wiring harness between defogger relay connector C-215 (terminal 4) and defogger connector F-16 (terminal 1) in good condition? 

    1. YES  : Go to Step 12.
    2. NO  : Repair or replace the wiring harness. Check that the defogger system works normally.
12. STEP 12. Check defogger relay connector C-215 and A/C-ECU connector C-16 for damage. 
    Fig 18: Checking A/C-ECU Connector C-16

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    Fig 19: Checking Defogger Relay Connector C-215

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    Q: Are defogger relay connector C-215 and A/C-ECU connector C-16 in good condition? 

    1. YES  : Go to Step 13.
    2. NO  : Repair or replace the connector. Check that the defogger system works normally.
13. STEP 13. Check the wiring harness between defogger relay connector C-215 (terminal 3) and A/C-ECU connector C-16 (terminal 1). 
    NOTE: Also check junction block connector C-214. If junction block connector C-214 is damaged, repair or replace the connector.
    Fig 20: Checking Wiring Harness A/C-ECU Connector C-16

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    Fig 21: Checking Wiring Harness Defogger Relay Connector C-215 & Junction Block Connector C-214

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    Q: Is the wiring harness between defogger relay connector C-215 (terminal 3) and A/C-ECU connector C-16 (terminal 1) in good condition? 

    1. YES  : Replace the A/C-ECU. The defogger should operate normally.
    2. NO  : Repair or replace the wiring harness. Check that the defogger system works normally.
14. STEP 14. Measure at defogger connector F-06 in order to check the ground circuit to the defogger connector. 
    1. Disconnect defogger connector F-06, and measure at the wiring harness side.
       Fig 22: Disconnecting Defogger Connector F-06

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    2. Measure the resistance value between terminal 1 and ground.
       • 2 ohm or less
    Fig 23: Measuring Resistance Value Between Terminal 1 & Ground

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    Q: Does the measured resistance value correspond with this range? 

    1. YES  : Go to  Step 17.
    2. NO  : Go to Step 15.
15. STEP 15. Check defogger connector F-06 for damage. 
    Fig 24: Checking Defogger Connector F-06

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    Q: Is defogger connector F-06 in good condition? 

    1. YES  : Go to Step 16.
    2. NO  : Repair or replace the connector. Check that the defogger system works normally.
16. STEP 16. Check the wiring harness between defogger connector F-06 (terminal 1) and ground. 
    Fig 25: Checking Wiring Harness Defogger Connector F-06

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    Q: Is the wiring harness between defogger connector F-06 (terminal 1) and ground in good condition? 

    1. YES  : Check that the defogger system works normally.
    2. NO  : Repair or replace the wiring harness. Check that the defogger system works normally.
17. STEP 17. Check the defogger. 
    1. Let the engine run at 2,000 r/min, and check the printed heater with the battery fully charged.
    2. Turn on the defogger switch, and use a voltmeter to measure the voltage in each printed heater at middle point A on the rear window glass.
       • The value should be approximately 6 volts.
    Fig 26: Measuring Voltage In Each Printed Heater Point A

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    Q: Does the defogger work normally? 

    1. YES  : Check that the defogger system works normally.
    2. NO  : Refer to REAR WINDOW DEFOGGER .