Mitsubishi Lancer (4A9 engine). Manual - part 300

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55A-81

(4) Voltage between terminal 1 and body earth

OK: System voltage

Q: Is the check result normal?

YES : 

Go to Step 27.

NO : 

Go to Step 21.

STEP 21. Measure the voltage at A-23X PTC 
heater relay3 connector.
(1) Remove the relay, and measure at the relay side.
(2) Voltage between terminal 4 and body earth

OK: System voltage

Q: Is the check result normal?

YES : 

Go to Step 23.

NO : 

Go to Step 22.

STEP 22. Check the wiring harness between A-
23X PTC heater relay3 connector terminal No. 4 
and fusible link (41) connector.

• Check the power supply line for open circuit.

Q: Is the check result normal?

YES : 

Intermittent malfunction (Refer to GROUP 

00 

− How to Use Troubleshooting/

Inspection Service Points - How to Cope 
with Intermittent Malfunction ).

NO : 

Repair the wiring harness.

STEP 23. Measure the voltage at A-23X PTC 
heater relay3 connector.
(1) Remove the relay, and measure at the relay side.
(2) Turn the ignition switch to the "ON" earth position.
(3) Voltage between terminal 1 and body earth

OK: System voltage

Q: Is the check result normal?

YES : 

Go to Step 25.

NO : 

Go to Step 24.

STEP 24. Check the wiring harness between A-
23X PTC heater relay3 connector terminal No. 1 
and C-317 ETACS-ECU connector terminal No. 5.
NOTE: Prior to the wiring harness inspection, check 
intermediate connector C-128, and repair if neces-
sary.

• Check the power supply line for open circuit.

Q: Is the check result normal?

YES : 

Intermittent malfunction (Refer to GROUP 

00 

− How to Use Troubleshooting/

Inspection Service Points - How to Cope 
with Intermittent Malfunction ).

NO : 

Repair the wiring harness.

STEP 25. Check the wiring harness wires 
between C-52 PTC heater connector terminal No. 
1 and A-23X PTC heater relay3 connector 
terminal No. 3.

• Check the power supply line for open circuit.

Q: Is the check result normal?

YES : 

Go to Step 26.

NO : 

Repair the wiring harness.

STEP 26. Check the wiring harness between A-
23X PTC heater relay3 connector terminal No. 2 
and C-15 A/C-ECU connector terminal No. 5.
NOTE: Prior to the wiring harness inspection, check 
intermediate connector C-127, and repair if neces-
sary.

• Check the power supply line for open circuit.

Q: Is the check result normal?

YES : 

Intermittent malfunction (Refer to GROUP 

00 

− How to Use Troubleshooting/

Inspection Service Points - How to Cope 
with Intermittent Malfunction ).

NO : 

Repair the wiring harness.

STEP 27. Connector check: C-53 PTC heater 
connector

Q: Is the check result normal?

YES : 

Go to Step 28.

NO : 

Repair the connector.

STEP 28. Resistance measurement at C-53 PTC 
heater connector.
(1) Disconnect the connector, and measure at the 

wiring harness side.

(2) Continuity between terminal 1, 2 and body earth.

OK: Continuity (Less than 2 ohms)

Q: Is the check result normal?

YES : 

Go to Step 30.

NO : 

Go to Step 29.

STEP 29. Check the wiring harness between C-53 
PTC heater connector (terminals 1 and 2) and 
body earth.

• Check the PTC heater earth line for open circuit.

Q: Is the check result normal?

YES : 

Intermittent malfunction (Refer to GROUP 

00 

− How to Use Troubleshooting/

Inspection Service Points - How to Cope 
with Intermittent Malfunction ).

NO : 

Repair the wiring harness.

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55A-82

STEP 30. Check the PTC heater.
Refer to .

Q: Is the check result normal?

YES : 

Replace the A/C-ECU.

NO : 

Replace the PTC heater.

DATA LIST REFERENCE TABLE

M1554005101032

Item No.

Check item

Inspection status

The display contents 
under normal condition

17

Engine speed

−

Displays correct engine 
speed.

19

Ambient temperature 
sensor

−

Ambient temperature is the 
same as M.U.T.-III 
displayed temperature

20

Air thermo sensor

−

Evaporator outlet 
temperature is the same as 
M.U.T.-III displayed 
temperature.

21

Interior temperature 
sensor

−

Interior temperature is the 
same as M.U.T.-III 
displayed temperature

23

Temperature setting

Displays air conditioner set 
temperature.

24

Engine coolant TEMP 
sensor

−

Engine coolant temperature 
is the same as M.U.T.-III 
displayed temperature.

26

Vehicle speed

−

Displays vehicle speed.

27

A/C Compressor drive 
request

Compressor ON

ON

Compressor OFF

OFF

28

Air conditioning switch

Air conditioner switch ON

ON

Air conditioner switch OFF

OFF

29

Refrigerant leak

−

Normal

34

Idle up request

−

Displays idle-up request 
signal.

45

In/out select damper 
poten (target)

−

Displays outside/inside air 
selection damper target 
position.

46

In/out select damp 
potentiometer

−

Displays outside/inside air 
selection damper position.

55

Air outlet c/o 
potentiometer

−

Displays air outlet 
changeover damper 
position.

56

Air outlet c/o potentio. 
(Target)

−

Displays air outlet 
changeover damper target 
position.

57

Low pressure

−

Normal

60

Rear defogger switch

Rear window defogger switch ON

ON

Rear window defogger switch OFF

OFF

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55A-83

61

Pressure sensor

−

Displays refrigerant 
pressure.

63

Air mix potentiometer

−

Displays the air mix damper 
position.

67

Photo sensor

−

Displays sunload.

68

Front blower fan

−

Displays blower motor 
condition.

69

Front blower fan 
(Target)

−

Displays blower motor 
target value.

73

Refrigerant pressure

−

Displays refrigerant 
pressure status.

74

Condenser fan

−

Displays condenser fan 
running condition.

76

Temp. set dial position

−

Displays the set 
temperature output value 
on the control panel.

77

A/C Panel type

−

Displays as same as the 
specification.

78

Fan set dial position

−

Displays the air volume 
output value on the control 
panel.

79

Air outlet c/o set dial 
position

−

Displays output value to the 
air outlet changeover dial 
on the control panel.

80*

Fan set dial operation 
flag

−

ON when the air volume 
adjusting dial is operated

81*

A/C SW operation flag

−

ON when the air conditioner 
switch is operated

82*

Temp. set dial operation 
flag

−

ON when the air conditioner 
switch is operated

83*

Defogger flag

−

ON when the air outlet 
changeover dial is set to the 
DEF position.

84*

In/out air c/o SW 
operation flag

−

ON when the inside air/
outside air changeover 
switch is operated

87*

Rear defogger SW 
operation flag

−

ON when the rear window 
switch is operated

88

Rear defogger SW lamp −

Displays rear window 
switch indicator status.

89

A/C SW lamp

−

Displays air conditioner 
switch indicator status.

Item No.

Check item

Inspection status

The display contents 
under normal condition

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55A-84

NOTE: *: The display may not switch if the switch 
operation timing does not correspond to the M.U.T.-
III readout timing.

ACTUATOR TEST TABLE

M1554005201200

Item No.

Check item

Driven content

2

Idle up request*

Idle-up request signal

5

In/out selection damper

The moving position of outside/inside air 
selection damper motor

6

Air mix damper motor

The moving position of air mix damper 
motor

7

Front blower fan

The amount of blower motor rotation

8

Air outlet c/o damper

Air outlet changeover damper motor 
moving position

10

Condenser fan*

The amount of condenser fan rotation

11

Air conditioner*

A/C switch selection position

12

Rear defogger switch*

Rear window defogger switch selection 
position

NOTE: *: When the engine is not running these func-
tion do not work.

CHECK AT A/C-ECU TERMINALS

M1552010302675

32

24

29

21

31

30

2223

27

35

33

25

34

26

36

28

AC507400

<C-15 (Vehicles with A/C)>

<C-13 (Vehicles with A/C)>

AN

<C-60 (Vehicles without A/C)>

<C-59 (Vehicles without A/C)>

90

In/out air c/o SW lamp

−

Displays the status of the 
inside air/outside air 
changeover switch 
indicator.

91

A/C Compressor drive 
flag

−

ON when the compressor is 
activated.

92

Wiper operation flag

−

ON when the wiper is 
operated.

93

Ignition position 
information

−

Ignition switch position 
status

94

Power source voltage

−

Displays power supply 
voltage.

95

IOD fuse equipment 
flag

−

IOD fuse status

Item No.

Check item

Inspection status

The display contents 
under normal condition

Terminal 
No.

Check item

Check condition

Normal condition

1

Power transistor (DRAIN)

Air volume control dial: Maximum air 
volume

0 to 2 V

2

Power transistor (GATE)

Air volume control dial: Maximum air 
volume

System voltage

3 

− 8

−

−

−