Mitsubishi 380. Manual - part 185

AUTO A/C DIAGNOSIS

HEATER, AIR CONDITIONING AND VENTILATION

55-36

DIAGNOSIS

Required Special Tool:

•  : Diagnostic Tool (MUT-III Sub Assembly)

• MB991824: Vehicle Communication Interface (V.C.I.)

• MB991827: MUT-III USB Cable

• MB991910: MUT-III Main Harness A (Vehicles with CAN 

communication system)

STEP 1. Using diagnostic tool , diagnose the CAN bus line.
Use diagnostic tool  to diagnose the CAN bus lines.
(1) Connect diagnostic tool  to the data link connector.
(2) Turn the ignition switch to "ON" position.
(3) Diagnose the CAN bus line.

Q: Is the check result satisfactory?

YES : Go to Step 2.
NO :  Repair the CAN bus lines. (Refer to GROUP 54C, 

Diagnosis-Can Bus Diagnostic Chart 

P.54C-405

). 

Then go to Step 7.

STEP 2. Recheck for diagnostic trouble code.
Recheck if the DTC is set.
(1) Erase the DTC.
(2) Turn the ignition switch to "ON" position.
(3) Check if the DTC is set.

Q: Is the check result satisfactory?

YES : It can be assumed that this malfunction is intermittent. 

Refer to GROUP 00, How to Use 
Troubleshooting/Inspection Service Points 

− How to 

Cope with Intermittent Malfunctions 

P.00-14

. 

NO :  Go to Step 3. 

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

AUTO A/C DIAGNOSIS

HEATER, AIR CONDITIONING AND VENTILATION

55-37

STEP 3. Using diagnostic tool , check actuator test item 42, 
43: air mix damper motor.

CAUTION

To prevent damage to diagnostic tool , always turn the 
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting diagnostic tool .
(1) Connect diagnostic tool  to the data link connector.
(2) Start the engine.
(3) Use diagnostic tool  to run the actuator test.

Item 42: air mix damper motor (0% MAX COOL position)
Item 43: air mix damper motor (100% MAX HOT position)

• Check that the air mixing damper control motor oper-

ates.

(4) Turn the ignition switch to the "LOCK" (OFF) position.

Q: Does the motor operate normally?

YES : Replace the A/C-ECU. Then go to Step 7.
NO :  Go to Step 4.

STEP 4. Check A/C-ECU connectors C-15 and air mixing 
damper control motor and potentiometer connector C-105 
for loose, corroded or damaged terminals, or terminals 
pushed back in the connector.
Q: Are A/C-ECU connectors C-15 and air mixing damper 

control motor and potentiometer connector C-105 in 
good condition?
YES : Go to Step 5.
NO :  Repair or replace the connector. Refer to GROUP 

00E, Harness Connector Inspection 

P.00E-2

. Then go 

to Step 7.

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

25DB147A

HARNESS SIDE

C-15

CONNECTORS: C-15, C-105

C-105

HARNESS SIDE

C-105

C-15 (B)

AUTO A/C DIAGNOSIS

HEATER, AIR CONDITIONING AND VENTILATION

55-38

STEP 5. Check the wiring harness between A/C-ECU 
connectors C-15 (terminal 1 and 2) and air mixing damper 
control motor and potentiometer connector C-105 
(terminals 1 and 2).
Q: Are the wiring harness between A/C-ECU connectors 

C-15 (terminals 1 and 2) and air mixing damper control 
motor and potentiometer connector C-105 (terminals 1 
and 2) in good condition?
YES : Go to Step 6.
NO :  Repair the wiring harness. Then go to Step 7.

25DB147A

HARNESS SIDE

C-15

CONNECTORS: C-15, C-105

C-105

HARNESS SIDE

C-105

C-15 (B)

AUTO A/C DIAGNOSIS

HEATER, AIR CONDITIONING AND VENTILATION

55-39

STEP 6. Check the air mixing damper control motor and 
potentiometer.

CAUTION

Do not apply battery voltage when the damper is in the 
MAX COOL or MAX HOT position.
Check the air mix damper control motor by the following proce-
dures.

Q: Are the air mixing damper control motor and 

potentiometer in good condition?
YES : Replace the A/C-ECU. Then go to Step 7.
NO :  Replace the air mixing damper control motor and 

potentiometer. Then go to Step 7.

LEVER POSITION BATTERY 

CONNECTION

LEVER 
OPERATION

At the MAX COOL 
position

• Connect 

terminal 2 to the 
positive battery 
terminal

• Connect 

terminal 1 to the 
negative battery 
terminal

The lever moves 
from the MAX 
COOL position to 
the MAX HOT 
position

At the MAX HOT 
position

• Connect 

terminal 1 to the 
positive battery 
terminal

• Connect 

terminal 2 to the 
negative battery 
terminal

The lever moves 
from the MAX HOT 
position to the MAX 
COOL position

25DB063A

MAX HOT POSITION

MAX COOL POSITION

1 2

4

3

5

7

6