Mitsubishi Galant (2004+). Manual - part 743

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-111

STEP 5. Recheck for diagnostic trouble code.

Check again if the DTC is set.
(1) Turn the ignition switch to the "ON" position.
(2) Check if the DTC is set.
(3) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the check result satisfactory?

YES : A poor connection, open circuit or other intermittent 

malfunction is present in the lines between the 
powertrain control module and the A/C-ECU (Refer to 
GROUP 00, How to Cope with Intermittent 
Malfunctions 

P.00-6

.)

NO :  Replace the A/C-ECU. On completion, check that the 

DTC is not reset.

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-112

SYMPTOM CHART <LOW TYPE>

M1552009900484

CAUTION

During diagnosis, a DTC code associated with 
other system may be set when the ignition switch 
is turned on with connector(s) disconnected. On 
completion, confirm all systems for DTC code(s). 
If DTC code(s) are set, erase them all.

SYMPTOM

INSPECTION 
PROCEDURE

REFERENCE 
PAGE

When the ignition switch is "ON", the A/C does not operate.

1.

P.55A-113

When the air outlet changeover control knob is moved to DEFROSTER or 
DEFROSTER/FOOT position, the A/C or the inside/outside air 
changeover damper motor does not operate.

2.

P.55A-114

Outside/Inside air changeover is not possible.

3.

P.55A-115

When the A/C is operating, temperature inside the passenger 
compartment does not decrease (cool air is not emitted).

4.

P.55A-121

Blower fan and motor do not turn.

5.

P.55A-140

Blower air amount cannot be changed.

6.

P.55A-152

The A/C indicator flashes.

7.

P.55A-156

Defogger function does not operate.

8.

P.55A-161

Defogger timer function does not operate.

9.

P.55A-172

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

10.

P.55A-173

Condenser fan does not operate.

11.

REFER TO 
GROUP 14 

− 

SYMPTOM 
CHART 

P.14-3

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-113

SYMPTOM PROCEDURES <LOW TYPE>

INSPECTION PROCEDURE 1: When the Ignition Switch is "ON", the A/C does not Operate.

.

TECHNICAL DESCRIPTION (COMMENT)
The blower system or the compressor system may 
be defective if there is no cool air coming from the 
vents.

.

TROUBLESHOOTING HINTS

• Malfunction of blower motor

• Malfunction of A/C compressor

DIAGNOSIS

Check that the blower motor operation when the blower 
switch is moved to the "HI" position.
(1) Turn the ignition switch to the "ON" position.
(2) Turn the blower switch to the "4" position
Q: Does the blower motor operate when the blower switch 

is moved to the "4" position?
YES : Refer to Inspection procedure 4 "When the A/C is 

operating, temperature inside the passenger 
compartment does not decrease (cool air not emitted) 

P.55A-121

."

NO :  Refer to Inspection procedure 5 "Blower fan and 

motor do not turn 

P.55A-140

."

MANUAL A/C DIAGNOSIS

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HEATER, AIR CONDITIONING AND VENTILATION

55A-114

INSPECTION PROCEDURE 2: When the Air Outlet Changeover Control Knob is Moved to 
DEFROSTER or DEFROSTER/FOOT Position, the A/C or the Inside/outside Air Changeover Damper 
Motor does not operate.

.

TECHNICAL DESCRIPTION (COMMENT)
If the outside/inside air selection damper control 
motor does not operate normally, the inside/outside 
air changeover damper motor system may be defec-
tive.

.

TROUBLESHOOTING HINTS

• Malfunction of the A/C-ECU

• Malfunction of the outside/inside air selection 

damper control motor

• Damaged harness wires or connectors

DIAGNOSIS

Check operation of the outside/inside air selection damper 
control motor.
(1) Turn the ignition switch to the "ON" position.
(2) Outside/inside air selection damper motor switch: This is 

used to switch from the inside air to outside air or vice 
versa.

(3) Check to see that the outside/inside air selection damper 

motor operates normally.

Q: Does outside/inside air selection damper control motor 

work normally?
YES : Replace the A/C-ECU.
NO :  Refer to Inspection procedure 3, "Inside/outside air 

changeover is not possible 

P.55A-115

."