Mitsubishi Lancer Evolution VI. Manual - part 125

FULL-AUTOMATIC AIR CONDITIONER – 

Troubleshooting

55-52

Inspection procedure 15

A/C-ECU power supply circuit check

NG

Repair

OK

Check the trouble symptom.

NG

Check the harness between the A/C-ECU and the fusible link
No.1, and repair if necessary.

OK

Check the trouble symptom.

NG

Check the harness between the A/C-ECU and the junction block,
and repair if necessary.

OK

Check the following connector:
B-05

NG

Repair

OK

Check the trouble symptom.

NG

Replace the A/C-ECU.

NG

Repair

OK

Check the trouble symptom.

NG

Check the harness between the A/C-ECU and the body earth,
and repair if necessary.

NG

Repair

OK

Measure at the A/C-ECU connector B-05.

D

Disconnect the connector, and measure at the harness
side connector.

D

Continuity between terminal (29) and body earth
OK: Continuity

D

Continuity between terminal (35) and body earth
OK: Continuity

NG

Check the following connectors:
B-05, B-48, B-19, B-69, B-80

OK

Measure at the A/C-ECU connector B-05.

D

Disconnect the connector, and measure at the harness
side connector.

D

Voltage between terminal (28) and body earth (Ignition
switch: ON)
OK: System voltage

NG

Check the following connectors:
B-49, B-75, B-76

Measure at the A/C-ECU connector B-04.

D

Disconnect the connector, and measure at the harness
side connector.

D

Voltage between terminal (3) and body earth
OK: System voltage

NG

Check the following connectors:
B-49, B-75, B-73

FULL-AUTOMATIC AIR CONDITIONER – 

Troubleshooting

55-53

Inspection procedure 16

A/C compressor control circuit check

Measure at the A/C-ECU connector B-05.

D

Blower switch and A/C switch: ON

D

Setting temperature: 17

_

C

D

Connect the connector.

D

Voltage between terminal (34) and body earth (Ignition
switch: ON)
OK: System voltage

NG

Check the following connector:
B-05

NG

Repair

OK

Check the trouble symptom.

NG

Replace the A/C-ECU.

OK

Measure at the A/C compressor relay connector A-116X.

D

Disconnect the connector, and measure at the harness
side connector.

D

Voltage between terminal (2) and body earth
OK: System voltage

NG

Check the following connectors:
A-49, B-15, B-05

NG

Repair

OK

Check the trouble symptom.

NG

Check the harness between the A/C-ECU and the A/C compressor
relay, and repair if necessary.

OK

Measure at the engine-ECU connector B-54 or B-59.

D

Disconnect the connector, and measure at the harness
side connector.

D

Voltage between terminal (21) or (22) and body earth
OK: System voltage

NG

Check the following connectors:
A-28, A-116X

NG

Repair

OK

Check the trouble symptom.

NG

Check the harness between the A/C compressor relay and the
engine-ECU, and repair if necessary.

OK

Replace the engine-ECU.

FULL-AUTOMATIC AIR CONDITIONER – 

Troubleshooting

55-54

DATA LIST REFERENCE TABLE

Check item

Check condition

Normal condition

Inside air temperature sensor

D

MUT

-II

 (11)

Ignition switch: ON

Inside air temperature and temper-
ature displayed on the MUT-

II

 are

identical.

Outside air temperature sen-
sor

D

MUT

-II

 (13)

Ignition switch: ON

Outside air temperature and tem-
perature displayed on the MUT-

II

are identical.

Heater water temperature
sensor

D

MUT

-II

 (15)

Ignition switch: ON

Heater core surface temperature
and temperature displayed on the
MUT-

II

 are identical.

Air thermo sensor

D

MUT

-II

 (21)

Ignition switch: ON

Evaporator surface temperature
and temperature displayed on the
MUT-

II

 are identical.

Photo sensor

D

MUT

-II

 (25)

Ignition switch: ON

Amount of incident light is propor-
tional to voltage displayed on the
MUT-

II

.

Air mix damper potentiometer

D

MUT

II

(31)

Ignition switch: ON

Damper position

Opening degree (%)

D

MUT

-II

  (31)

MAX. HOT

Approx. 100

MAX. COOL

Approx. 0

Air outlet changeover damper
potentiometer

Ignition switch: ON

Damper position

Opening degree (%)

potentiometer

D

MUT

-II

 (32)

FACE

Approx. 0

FOOT

Approx. 50

FOOT/DEF.

Approx. 75

DEF.

Approx. 100

CHECK AT THE A/C-ECU TERMINALS

A/C-ECU

The parenthesized values in “Normal condition” column are for your reference.

Terminal
No.

Check item

Check condition

Normal condition

1

Front power transistor collector output

When blower switch is at OFF

System voltage

When blower switch is at LO

Approx. 7 V

When blower switch is at HI

Almost no voltage (0 V)

2

Front power transistor base output

When blower switch is at OFF

0 V

When blower switch is at LO

Approx. 1.3 V

When blower switch is at HI

Approx. 2.5 V

3

Backup

At all times

System voltage

FULL-AUTOMATIC AIR CONDITIONER – 

Troubleshooting

55-55

Terminal
No.

Normal condition

Check condition

Check item

4

Heater water temperature sensor
input

When sensor section temperature is
25

_

C (4 k

Ω

)

2.3 – 2.9 V

5

Air mix damper potentiometer input

When damper is moved to MAX. HOT
position

4.7 – 5.0 V

6

Air outlet changeover damper poten-
tiometer input

When damper is moved to DEF.
position

4.8 – 5.2 V

7

Outside air temperature sensor input

When sensor section temperature is
25

_

C (4 k

Ω

)

2.3 – 2.9 V

8

Air thermo sensor input

When sensor section temperature is
25

_

C (4 k

Ω

)

2.3 – 2.9 V

9

Photo sensor (–)

At luminous intensity of 0 lux

0 V

At luminous intensity of 100,000 lux or
more

–0.1 – 0.2 V

10

Sensor power supply

At all times

4.8 – 5.2 V

12

Blower motor HI relay (Exciting circuit)

When blower switch is in HI

1.5 V or less

When blower switch is in a position
other than HI

System voltage

16

Rear defogger

When rear defogger switch is ON

1.5 V or less

When rear defogger switch is OFF

System voltage

17

Diagnosis date output

When ignition switch is ON

0 V 

↔

 12 V

18

Diagnosis control output

When ignition switch is ON

System voltage – 2 V

19

Photo sensor (+)

At all times

0 V

20

Sensor earth

At all times

0 V

21

Air outlet changeover damper motor
(FACE)

When damper is moved to FACE
position

10 V

When damper is moved to DEF.
position

Almost no voltage 
(0.5 V)

22

Air mix damper motor (MAX. COOL)

When damper is moved to MAX.
COOL position

10 V

When damper is moved to MAX. HOT
position

Almost no voltage 
(0.5 V)

23

Inside/outside air changeover damper
motor (Inside)

When switch is set to inside air
position

Almost no voltage 
(0.5 V)

When switch is set to outside air
position

10 V

24

Air outlet changeover damper motor
(DEF.)

When damper is moved to FACE
position

Almost no voltage 
(0.5 V)

When damper is moved to DEF.
position

10 V