Mitsubishi Evolution X. Manual - part 1089

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CHASSIS ELECTRICAL

54A-717

TECHNICAL DESCRIPTION (COMMENT)

The rear window defogger is able to turn on while engine is run-
ning. 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 GROUP 55 - Inspection procedure 2, 

"Malfunction of the A/C-ECU power supply system 

P.55-74

."

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 GROUP 

00E, Harness Connector Inspection 

P.00E-2

. The 

rear window defogger system should work normally.

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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 GROUP 

00E, Harness Connector Inspection 

P.00E-2

. 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.

Battery voltage

Terminal 
number

Normal condition

With no current applied

3 

− 4

No continuity

With current applied 

 

[terminal 1 (+), terminal 2 (

−)]

Continuity exists 

 

(2 

Ω or less)

AC609147

2

3

4

1

AB

Rear window
defogger relay

AC709325 AQ

Harness side: F-29

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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, cor-
roded, 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 GROUP 00E, Harness 
Connector Inspection 

P.00E-2

.

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.

AC709325 AR

Harness side: C-306

AC709325 AS

Harness side: C-306

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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 GROUP 

00E, Harness Connector Inspection 

P.00E-2

. 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 

GROUP 00E, Harness Connector Inspection 

P.00E-2

. Check that the rear window defogger 

system works normally.