Rear Window Defogger Does Not Operate.

Rear Window Defogger Does Not Operate.

Rear Window Defogger Circuit:

A/C Control Panel Circuit:

TECHNICAL DESCRIPTION (COMMENT)
The rear window defogger is able to turn on while engine is running. If the defogger does not operate when the rear window defogger switch is turned on, the rear window defogger relay system may be defective.

TROUBLESHOOTING HINTS
- The A/C-ECU may be defective.
- The rear window defogger relay may be defective.
- The A/C control panel may be defective.
- Damaged harness wires or connectors

DIAGNOSIS

Required Special Tools:
- MB991223: Harness Set
- MB992006: Extra Fine Probe

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

1. Turn the ignition switch to the "ON" position.
2. Check the engine running.
3. Check the operations of rear window defogger and A/C.

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

YES : Go to Step 2.

NO : Refer to Heater and A/C and Ventilation -Inspection procedure 2, "Malfunction of the A/C-ECU power supply system." Inspection Procedure 2

STEP 2. Check rear window defogger relay connector C-306 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q : Is rear window defogger relay connector C-306 in good condition?

YES : Go to Step 3.

NO : Repair or replace the connector. Refer to General (Electrical), Harness Connector Inspection. The rear window defogger system should work normally.

STEP 3. Check the rear window defogger relay continuity.

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






Q : Is the rear window defogger relay in good condition?

YES : Go to Step 4.

NO : Replace the rear window defogger relay. The rear window defogger system should work normally.

STEP 4. Check rear window defogger connector F-29 and A/C control panel connector C-123 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q : Are rear window defogger connector F-29 and A/C control panel connector C-123 in good condition?

YES : Go to Step 5.

NO : Repair or replace the connector. Refer to General (Electrical), Harness Connector Inspection. The rear window defogger system should work normally.

STEP 5. Measure the voltage at rear window defogger connector F-29.

1. Disconnect rear window defogger connector F-29, and measure the voltage at the harness side.
2. Turn the ignition switch to the "ON" position.




3. Measure the voltage between rear window defogger connector F-29 terminal No.1 and ground.
- The measured value should be approximately 12 volts (battery positive voltage).

Q : Is the measured voltage approximately 12 volts?

YES : Go to Step 13.

NO : Go to Step 6.

STEP 6. Measure the voltage at rear window defogger relay connector C-306.

1. Disconnect rear window defogger relay connector C-306, and measure the voltage at the junction block side.




2. Measure the voltage between terminal 4 and ground.
- The measured value should be approximately 12 volts (battery positive voltage).

Q : Is the measured voltage approximately 12 volts?

YES : Go to Step 8.

NO : Go to Step 7.

STEP 7. Check the wiring harness between rear window defogger relay connector C-306 (terminal 4) and the fusible link (37).

NOTE: Also check intermediate connector C-132 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connector C-132 is damaged, repair or replace the connector as described in General (Electrical), Harness Connector Inspection.

Q : Is the wiring harness between rear window defogger relay connector C-306(terminal 4) and the fusible link (37) in good condition?

YES : Check that the rear window defogger system works normally.

NO : Repair the wiring harness. Check that the rear window defogger system works normally.

STEP 8. Measure the voltage at rear window defogger relay connector C-306.

1. Disconnect rear window defogger relay connector C-306, and measure the voltage at the junction block side.
2. Turn the ignition switch to the "ON" position.




3. Measure the voltage between terminal 1 and ground.
- The measured value should be approximately 12 volts (battery positive voltage).

Q : Is the measured voltage approximately 12 volts?

YES : Go to Step 11.

NO : Go to Step 9.

STEP 9. Check ETACS-ECU connector C-301 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q : Is ETACS-ECU connector C-301 in good condition?

YES : Go to Step 10.

NO : Repair or replace the connector. Refer to General (Electrical), Harness Connector Inspection. Check that the rear window defogger system works normally.

STEP 10. Check the wiring harness between rear window defogger relay connector C-306 (terminal 1) and ETACS-ECU C-301 (terminal 12).

Q : Is the wiring harness between rear window defogger relay connector C-306 (terminal 1) and ETACS-ECU connector C-301 (terminal 12) in good condition?

YES : Check that the rear window defogger system works normally.

NO : Repair the wiring harness. Check that the rear window defogger system works normally.

STEP 11. Check the wiring harness between rear window defogger relay connector C-306 (terminal 2) and A/C-ECU connector C-123 (terminal 6).

Q : Is the wiring harness between rear window defogger relay connector C-306 (terminal 2) and A/C-ECU connector C-123 (terminal 6) in good condition?

YES : Go to Step 12.

NO : Repair or replace the wiring harness. Refer to General (Electrical), Harness Connector Inspection. Check that the rear window defogger system works normally.

STEP 12. Check the wiring harness between rear window defogger relay connector C-306 (terminal 3) and rear window defogger connector F-29 (terminal 1).

NOTE: Also check intermediate connectors C-42 and D-16, and joint connector C-102 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connectors C-42 and D-16, and joint connector C-102 is damaged, repair or replace the connector as described in General (Electrical), Harness Connector Inspection.

Q : Is the wiring harness between rear window defogger relay connector C-306 (terminal 3) and rear window defogger connector F-29 (terminal 1) in good condition?

YES : It can be assumed that this malfunction is intermittent. Refer to General (Body and Chassis), How to Use Troubleshooting/Inspection Service Points -How to Cope with Intermittent Malfunctions.

NO : Repair or replace the wiring harness. Refer to General (Electrical), Harness Connector Inspection. Check that the rear window defogger system works normally.

STEP 13. Check rear window defogger connector F-03 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q : Is rear window defogger connector F-03 in good condition?

YES : Go to Step 14.

NO : Repair or replace the connector. Refer to General (Electrical), Harness Connector Inspection. Check that the rear window defogger system works normally.

STEP 14. Measure the resistance at rear window defogger connector F-03.

1. Disconnect rear window defogger connector F-03, and measure at the wiring harness side.




2. Measure the resistance between terminal 1 and ground.
- The measured value should be 2 ohms or less.

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

YES : Go to Step 16.

NO : Go to Step 15.

STEP 15. Check the wiring harness between rear window defogger connector F-03 (terminal 1) and the ground.

Q : Is the wiring harness between rear window defogger connector F-03 (terminal 1) and the ground in good condition?

YES : Check that the rear window defogger system works normally.

NO : Repair or replace the wiring harness. Refer to General (Electrical), Harness Connector Inspection. Check that the rear window defogger system works normally.

STEP 16. Check A/C-ECU connector C-22 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q : Is A/C-ECU connector C-22 in good condition?

YES : Go to Step 17.

NO : Repair or replace the connector. Refer to General (Electrical), Harness Connector Inspection. Check that the rear window defogger system works normally.

STEP 17. Check the wiring harness between A/C-ECU connector C-22 (terminals 9 and 10) and A/C control panel connector C-123 (terminals 1 and 9).

Q : Are the wiring harness between A/C-ECU connector C-22 (terminals 9 and 10) and A/C control panel connector C-123 (terminals 1 and 9) in good condition?

YES : Go to Step 18.

NO : Repair or replace the wiring harness. Refer to General (Electrical), Harness Connector Inspection. Check that the rear window defogger system works normally.

STEP 18. Check the rear window 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 rear window 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.

Q : Does the rear window defogger work normally?

YES : Go to Step 19.

NO : Repair the rear window defogger.

STEP 19. Replace the A/C control panel and check the trouble symptom again Check the trouble symptom again.

Q : Is the check result satisfactory?

YES : The procedure is complete.

NO : Replace the A/C-ECU.