Mitsubishi Evolution X. Manual - part 1280

AUTO A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55-71

SYMPTOM CHART

M1552009900729

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 A/C is operation, temperature inside the passenger 
compartment does not decrease (Cool air is not emitted).

1

P.55-72

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

2

P.55-74

The compressor does not work.

3

P.55-78

Blower fan and motor do not turn.

4

P.55-85

Blower air amount cannot be changed.

5

P.55-90

Outside/inside air changeover is not possible.

6

P.55-93

A/C outlet air temperature does not increase.

7

P.55-95

Air outlet vent cannot be changed.

8

P.55-98

Blower motor power supply system.

9

P.55-101

AUTO A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55-72

SYMPTOM PROCEDURES

INSPECTION PROCEDURE 1: When the A/C is Operation, Temperature Inside the Passenger 
Compartment does not Decrease (Cool Air is not Emitted).

.

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-ECU

• Malfunction of A/C compressor

DIAGNOSIS

STEP 1. Using scan tool MB991958, read the diagnostic 
trouble code.

CAUTION

To prevent damage to scan tool MB991958, always turn the 
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991958.
Check if an A/C-ECU DTC is set.
(1) Connect scan tool MB991958. Refer to "How to connect the 

Scan Tool (M.U.T.-III) 

P.55-7

."

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

YES : Refer to Diagnostic Trouble Code Chart 

P.55-9

.

NO :  Go to Step 2.

STEP 2. Check that the blower motor operation when the 
blower knob is moved to the "Maximum air volume" 
position.
(1) Turn the ignition switch to the "ON" position.
(2) Turn the blower knob to the "Maximum air volume" position
Q: Does the blower motor operate when the blower knob is 

moved to the "Maximum air volume" position?
YES : Go to Step 3.
NO :  Refer to Inspection procedure 4 "Blower fan and 

motor do not turn 

P.55-85

."

AC608435

Data link connector

MB991827

MB991824

MB991910

AB

AUTO A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55-73

STEP 3. Check the rear window defogger and 
outside/inside air selection damper control motor 
operation.
(1) Turn the ignition switch to the "ON" position.
(2) Check the engine running.
(3) Check the operations of rear window defogger and 

outside/inside air selection damper control motor.

Q: Do the rear window defogger and outside/inside air 

selection damper control motor work normally?
YES : Refer to Inspection procedure 3 "The A/C compressor 

does not Work 

P.55-78

."

NO :  Refer to Inspection procedure 2, "Malfunction of the 

A/C-ECU power supply system 

P.55-74

."

AUTO A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55-74

INSPECTION PROCEDURE 2: Malfunction of the A/C-ECU Power Supply System.

.

A/C-ECU Power Supply Circuit

IGNITION
SWITCH (IG1)

A/C-ECU

ETACS
-ECU

RELAY BOX
(ENGINE
COMPARTMENT)

POWER
SUPPLY

POWER
SUPPLY

IG1
RELAY

FUSIBLE
LINK

34

FUSIBLE
LINK

36

AC708617

AC708951AO

Connector: C-22

C-22 (B)

AC708972AB

Connector: C-317

Junction block