Mitsubishi Galant (2004+). Manual - part 755

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-159

STEP 4. Check the A/C pressure sensor.

1. Assemble a gauge manifold on the high pressure service 

valve.

2. Disconnect the A/C pressure sensor connector and connect 

special tool test harness MB991658 as shown in the illustra-
tion.

3. Turn ON the engine and then turn ON the air conditioner 

switch.

4. At this time, check to see that the voltage of A/C pressure 

sensor terminal No. 2 reflects the specifications of the fig-
ure.
NOTE: The allowance shall be defined as 

±

5%.

Q: Is the A/C pressure sensor in good condition?

YES : Go to Step 5.
NO :  Replace the A/C pressure sensor. Check that the air 

conditioning works normally. 

STEP 5. Check A/C-ECU connector C-10 for loose, 
corroded or damaged terminals, or terminals pushed back 
in the connector.

Q: Is A/C-ECU connectors C-10 in good condition?

YES : Go to Step 6.
NO :  Repair or replace the connector. Refer to GROUP 

00E, Harness Connector Inspection 

P.00E-2

. Check 

that the air conditioning works normally. 

AC305034

A/C PRESSURE SENSOR

AD

AC307368

A/C 
PRESSURE 
SENSOR 
SIDE

MB991658

AB

HARNESS SIDE

AC208297AB

REFRIGERANT PRESSURE (MPa)

OUTPUT VOLTAGE 

(V)

0

1

2

3

5

4

1

2

3

AC305233AW

CONNECTOR: C-10

HARNESS SIDE

C-10 (B)

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-160

STEP 6. Check the wiring harness between A/C-ECU 
connector C-10 (terminals 4, 1 and 3) and A/C pressure 
sensor connector A-30 (terminals 2, 1 and 3).

NOTE: Also check intermediate connector C-29 for loose, cor-
roded, or damaged terminals, or terminals pushed back in the 
connector. If intermediate connector C-29 is damaged, repair or 
replace the connector as described in GROUP 00E, Harness 
Connector Inspection 

P.00E-2

.

Q: Is the wiring harness between A/C-ECU connector C-10 

(terminals 4, 1 and 3) and A/C pressure sensor 
connector A-30 (terminals 2, 1 and 3) in good condition?
YES : Replace the A/C-ECU. Check that the air conditioning 

works normally. 

NO :  Repair the wiring harness. Check that the air 

conditioning works normally. 

STEP 7. Check the refrigerant level.

Use the refrigerant recovery station to remove all of the refrig-
erant, and then calculate the amount of the refrigerant and 
charge it.
Q: Is the refrigerant level correct?

YES : Replace the A/C-ECU.
NO :  Correct the refrigerant level (Refer to On-vehicle 

Service

P.55A-266

). Check that the air conditioning 

works normally. 

AC305233AW

CONNECTOR: C-10

HARNESS SIDE

C-10 (B)

AC305206

CONNECTOR: A-30

AY

HARNESS SIDE

A-30 (B)

AC305231AI

CONNECTOR: C-29

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-161

INSPECTION PROCEDURE 8: Defogger Function Does Not Operate.

IGNITION
SWITCH (IG2)

1

FUSIBLE 
LINK

DEFOGGER
RELAY

CHOKE
COIL

JUNCTION
BLOCK

DEFOGGER

A/C-
ECU

Defogger Circuit

MANUAL A/C DIAGNOSIS

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HEATER, AIR CONDITIONING AND VENTILATION

55A-162

.

TECHNICAL DESCRIPTION (COMMENT)
If the defogger does not operate when the defogger 
switch is turned on, the defogger relay system may 
be defective.

.

TROUBLESHOOTING HINTS

• Malfunction of the A/C-ECU

• Malfunction of the defogger relay

• Damaged harness wires or connectors

DIAGNOSIS

Required Special Tool:

• MB991223: Test Harness Set

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

control motor work normally?
YES : Go to Step 2.
NO :  Refer to Inspection procedure 10, "Malfunction of the 

A/C-ECU power supply system

P.55A-173

."

AC305233

CONNECTOR: C-09

BS

C-09 (B)

AC305231CH

CONNECTOR: C-29

AC207120

C-216 (B)

CONNECTORS: C-201, C-204, C-211, C-215, 
C-216

C-201

C-215

C-211

AZ

C-204

AC305268

CONNECTORS: D-08, D-11, D-13, D-14

D-08

D-11

D-13

D-14

AL