Mitsubishi L200. Manual - part 873

TROUBLESHOOTING

AUTOMATIC AIR CONDITIONER

55B-21

DIAGNOSIS PROCEDURE

STEP 1. Connector check: C-43 A/C-ECU 
connector and C-38 mode selection damper 
control motor and potentiometer connector

AC509611AR

Connector: C-43 <LHD>

Harness side

AC509932AS

Harness side

Connector: C-43 <RHD>

AC509613BA

C-38 (B)

Harness side

Connector: C-38 <LHD>

AC509930 AZ

C-38 (B)

Harness side

Connector: C-38 <RHD>

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Repair the connector.

STEP 2. Check the wiring harness between C-43 
A/C-ECU connector (terminals 12 and 1) and C-38 
mode selection damper control motor and 
potentiometer connector (terminals 1 and 3).

AC509611AR

Connector: C-43 <LHD>

Harness side

AC509932AS

Harness side

Connector: C-43 <RHD>

AC509613BA

C-38 (B)

Harness side

Connector: C-38 <LHD>

AC509930 AZ

C-38 (B)

Harness side

Connector: C-38 <RHD>

• Check the motor activating lines for open and 

short circuit.

Q: Is the check result normal?

YES : 

Go to Step 3.

NO : 

Repair the wiring harness.

TROUBLESHOOTING

AUTOMATIC AIR CONDITIONER

55B-22

STEP 3. Check the mode selection damper 
control motor and potentiometer.
Refer to 

P.55B-97

.

Q: Is the check result normal?

YES : 

Go to Step 4.

NO : 

Replace the mode selection damper control 
motor and potentiometer.

STEP 4. M.U.T.-III diagnosis code

Q: Is the diagnosis code set?

YES : 

Replace the automatic air conditioner 

control panel (A/C-ECU).

NO : 

The trouble can be an intermittent 
malfunction (Refer to GROUP 00, How to 
Cope with Intermittent Malfunction ).

TROUBLE SYMPTOM CHART

M1554005001875

Trouble symptom

Inspection procedure 
number

Reference page

Cool air does not come

1

P.55B-23

The blower does not work

2

P.55B-32

The blower air volume cannot be changed

3

P.55B-41

The inside/outside air changeover is impossible

4

P.55B-45

The A/C compressor does not work

5

P.55B-49

The rear window defogger does not work <Vehicles 
without rear panel power window>

6

P.55B-55

The rear window defogger does not work <Vehicles with 
rear panel power window>

7

P.55B-65

The PTC heater does not work

8

P.55B-72

A/C ECU power supply system

9

P.55B-87

The outlet air temperature can not be changed even if 
the amount of solar radiation changes

10

P.55B-87

Condenser fan does not operate

11

Refer to GROUP 55A, 
trouble symptom chart 

TROUBLESHOOTING

AUTOMATIC AIR CONDITIONER

55B-23

SYMPTOM PROCEDURES

Inspection Procedure 1: Cool air does not come

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

A/C-ECU System Circuit

ENGINE-ECU

A/C-ECU

DUAL 
PRESSURE 
SWITCH

LOW-PRESSURE 
SIDE

HIGH-PRESSURE 
SIDE

BLOWER 
RELAY

BLOWER 
MOTOR

POWER 
TRANSISTOR

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

A/C Compressor and Clutch Assembly Circuit

IGNITION 
SWITCH (IG2)

RELAY 
BOX

A/C COMPRESSOR 
RELAY

A/C 
COMPRESSOR 
AND CLUTCH 
ASSEMBLY

ENGINE-ECU

FUSIBLE 
LINK

20

A/C 
COMPRESSOR 
CLUTCH ASSEMBLY

TROUBLESHOOTING

AUTOMATIC AIR CONDITIONER

55B-24

COMMENTS ON TROUBLE SYMPTOM
The blower system, the compressor system or the 
communication system between the engine-ECU 
and the A/C-ECU may be defective if there is no cool 
air coming from the spit hole.

PROBABLE CAUSES

• Malfunction of air thermo sensor

• Malfunction of dual pressure switch

• Damaged harness wires and connectors

• Malfunction of engine-ECU

• Malfunction of the automatic A/C control panel (A/

C-ECU)