Mitsubishi Lancer (4A9 engine). Manual - part 290

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55A-41

INSPECTION PROCEDURE 4: The Inside/Outside Air Changeover is impossible.

OUTSIDE/INSIDE AIR
SELECTION DAMPER 
CONTROL MOTOR

HEATER CONTROL UNIT

Outside/Inside Air Selection Damper Control Motor Circuit

Wire colour code 
B : Black     LG : Light green     G : Green     L : Blue     W : White     Y : Yellow     SB : Sky blue 
BR : Brown     O : Orange     GR : Grey     R : Red     P : Pink     V : Violet     PU : Purple     SI : Silver

AC801343

Heater Control Panel Circuit

HEATER 
CONTROL 
UNIT

HEATER 
CONTROL 
PANEL

CPU

INTERFACE
CIRCUIT

Wire colour code 
B : Black     LG : Light green     G : Green     L : Blue     W : White     Y : Yellow     SB : Sky blue 
BR : Brown     O : Orange     GR : Grey     R : Red     P : Pink     V : Violet     PU : Purple     SI : Silver

ACA00851

AC612706

Connectors: C-59, C-60, C-107, C-147 <LHD>

BR

C-60 (B)

C-107

C-110

C-59 (B)

C-147

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55A-42

COMMENTS ON TROUBLE SYMPTOM
If the air recirculation cannot be changed by using 
the inside air/outside air changeover switch, the 
inside air/outside air changeover motor system may 
be faulty.

PROBABLE CAUSES

• Malfunction of the outside/inside air selection 

damper control motor

• Malfunction of the heater control panel

• Damaged wiring harness or connectors

• Malfunction of the heater control unit

DIAGNOSIS PROCEDURE

STEP 1. Check the operation of the heater control 
panel
Check that the rear window defogger switch and air 
volume control dial can operate.

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

INSPECTION PROCEDURE 9: Refer to 
heater control unit power supply system  .

STEP 2. M.U.T.-III diagnosis code
Check that the diagnosis code related to the air con-
ditioner is not set.

Q: Is the diagnosis code set?

YES : 

Carry out the diagnosis code procedures. 

Refer to .

NO : 

Go to Step 3.

STEP 3. M.U.T.-III actuator test
Carry out the actuator test. (Refer to ).

• Item 05: In/out selection damper (Select "position 

reset".)

Q: Does the blower motor work normally?

YES : 

This diagnosis is complete.

NO : 

Go to Step 4.

STEP 4. Connector check: C-147 heater control 
panel connector and C-60 heater control unit 
connector

Q: Is the check result normal?

YES : 

Go to Step 5.

NO : 

Repair the connector.

STEP 5. Check the wiring harness between C-147 
heater control panel connector terminal No. 9 
and C-60 heater control unit connector terminal 
No. 9. 

• Check the heater control panel signal line for 

open or short circuit.

Q: Is the check result normal?

YES : 

Go to Step 6.

NO : 

Repair the wiring harness.

STEP 6. Connector check: C-59 heater control 
unit connector and C-107 outside/inside air 
selection damper control motor connector

Q: Is the check result normal?

YES : 

Go to Step 7.

NO : 

Repair the connector.

STEP 7. Check the wiring harness between C-59 
heater control unit connector (terminals 29, 24, 
27, 25 and 26) and C-107 outside/inside air 
selection damper control motor connector 
(terminals 3, 1, 4, 5 and 2).

• Check the heater control unit signal line and earth 

line for open or short circuit.

Q: Is the check result normal?

YES : 

Go to Step 8.

NO : 

Repair the wiring harness.

STEP 8. Replace the air outside/inside air 
circulation switching damper motor, and then 
recheck the trouble symptom.
 Check to see that the outside air/inside air circula-
tion switching damper motor operates normally.
NOTE: Whenever the motor is replaced, initialise the 
motor position by using the Actuator Test.

Q: Is the check result normal?

YES : 

This diagnosis is complete.

NO : 

Replace the heater control unit.

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55A-43

INSPECTION PROCEDURE 5: Outlet air temperature cannot be set

Air Mixing Damper Control Motor Circuit

HEATER CONTROL UNIT

AIR MIXING
DAMPER
CONTROL MOTOR

Wire colour code 
B : Black     LG : Light green     G : Green     L : Blue     W : White     Y : Yellow     SB : Sky blue 
BR : Brown     O : Orange     GR : Grey     R : Red     P : Pink     V : Violet     PU : Purple     SI : Silver

AC801344

AC612706

Connectors: C-59, C-117 <LHD>

BS

C-59 (B)

C-117

COMMENTS ON TROUBLE SYMPTOM
If the air conditioner outlet temperature cannot be 
adjusted, the air mixing damper control motor or the 
heater control unit may be faulty.
NOTE: It cannot be adjusted while the engine cool-
ant temperature is low.

PROBABLE CAUSES

• Malfunction of the air mix damper control motor

• Malfunction of the heater control unit

DIAGNOSTIC PROCEDURE

STEP 1. M.U.T.-III diagnosis code
Check that the diagnosis code related to the air con-
ditioner is not set.

Q: Is the diagnosis code set?

YES : 

Carry out the diagnosis code procedures. 

Refer to .

NO : 

Go to Step 2.

STEP 2. M.U.T.-III actuator test
Carry out the actuator test. (Refer to ).

• Item 06: air mixing damper control motor (Select 

"position reset").

Q: Is the check result normal?

YES : 

This diagnosis is complete.

NO : 

Go to Step 3.

STEP 3. Connector check: C-117 air mixing 
damper control motor connector, C-59 heater 
control unit connector

Q: Is the check result normal?

YES : 

Go to Step 4.

NO : 

Repair the connector concerned.

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55A-44

STEP 4. Check the wiring harness wires between 
C-117 air mixing damper control motor connector 
(terminals 3, 2, 5, 4 and 1) and C-59 heater control 
unit connector (terminals 29, 35, 36, 34 and 28).

• Check the input line for open circuit.

Q: Is the check result normal?

YES : 

Go to Step 5.

NO : 

Repair the wiring harness.

STEP 5. Replace the air mixing damper control 
motor, and recheck the trouble symptom.
Check that outlet air temperature can be adjusted.
NOTE: Whenever the motor is replaced, initialise the 
motor position by using the Actuator Test.

Q: Is the check result normal?

YES : 

This diagnosis is complete.

NO : 

Replace the heater control unit.

INSPECTION PROCEDURE 6: Air outlets changeover is impossible.

Mode Selection Damper Control Motor  Circuit

MODE SELECTION 
DAMPER CONTROL
MOTOR

Wire colour code 
B : Black     LG : Light green     G : Green     L : Blue     W : White     Y : Yellow     SB : Sky blue 
BR : Brown     O : Orange     GR : Grey     R : Red     P : Pink     V : Violet     PU : Purple     SI : Silver

HEATER CONTROL UNIT

AC801345

AC612706

Connectors: C-59, C-108 <LHD>

BT

C-59 (B)

C-108

COMMENTS ON TROUBLE SYMPTOM
If the air conditioner outlets changeover is impossi-
ble, the mode selection damper control motor or the 
heater control unit may be faulty.

PROBABLE CAUSES

• Malfunction of the mode selection damper control 

motor

• Malfunction of the heater control unit

DIAGNOSTIC PROCEDURE

STEP 1. M.U.T.-III diagnosis code
Check that the diagnosis code related to the air con-
ditioner is not set.

Q: Is the diagnosis code set?

YES : 

Carry out the diagnosis code procedures. 

Refer to .

NO : 

Go to Step 2.