Mitsubishi L200. Manual - part 886

TROUBLESHOOTING

AUTOMATIC AIR CONDITIONER

55B-73

NOTE: When the coolant temperature becomes 
above 80 degrees celsius and PTC heater stops the 
operation, the PTC heater does not operate until 
coolant temperature becomes below 70 degrees cel-
sius.

PROBABLE CAUSES

• Malfunction of the heater switch system

• Damaged the wiring harness or connectors

• Malfunction of the PTC heater relay 1

• Malfunction of the PTC heater relay 2

• Malfunction of the PTC heater 1

• Malfunction of the PTC heater 2

DIAGNOSIS PROCEDURE

STEP 1. Connector check: C-149 PTC heater 1 
connector

AC509613AT

Harness side

Connector: C-149 <LHD>

C-149 (GR)

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

Repair the connector.

STEP 2. Resistance measurement at the C-149 
PTC heater 1 connector.

AC509613AT

Harness side

Connector: C-149 <LHD>

C-149 (GR)

(1) Disconnect the connector, and measure at the 

wiring harness side.

AC310506HU

Connector C-149 
(Harness side)

(2) Continuity between terminal 1 and body earth

OK: Continuity (Less than 2

Ω)

Q: Is the check result normal?

YES : 

Go to Step 4.

NO : 

Go to Step 3.

STEP 3. Check the wiring harness between C-149 
PTC heater 1 connector terminal No.1 and body 
earth.

AC509613AT

Harness side

Connector: C-149 <LHD>

C-149 (GR)

• Check the PTC heater earth line for open circuit.

Q: Is the check result normal?

YES : 

The trouble can be an intermittent 

malfunction (Refer to GROUP 00, How to 
Cope with Intermittent Malfunction .)

NO : 

Repair the wiring harness.

STEP 4. Resistance measurement at the C-150 
PTC heater 2 connector.

AC509613 AU

Harness side

Connector: C-150 <LHD>

C-150 (GR)

(1) Disconnect the connector, and measure at the 

TROUBLESHOOTING

AUTOMATIC AIR CONDITIONER

55B-74

wiring harness side.

AC310506HV

Connector C-150 
(Harness side)

(2) Continuity between terminal 1 and body earth

OK: Continuity (Less than 2

Ω)

Q: Is the check result normal?

YES : 

Go to Step 6.

NO : 

Go to Step 5.

STEP 5. Check the wiring harness between C-150 
PTC heater 2 connector terminal No.1 and body 
earth.

AC509613 AU

Harness side

Connector: C-150 <LHD>

C-150 (GR)

• Check the PTC heater earth line for open circuit.

Q: Is the check result normal?

YES : 

The trouble can be an intermittent 

malfunction (Refer to GROUP 00, How to 
Cope with Intermittent Malfunction .)

NO : 

Repair the wiring harness.

STEP 6. Connector check: C-105 engine-ECU 
connector

AC509613 CD

Harness side

C-105 (B)

Connector: C-105 <LHD>

35

40

41

42

1817

38

39

15

16

14

3736

12

13

11

32

8

3433

9

10

30

31

7 6

29

5

4

28

3

27

2

26

1

25

19
43

2120

22

23

46

47

4544

24
48

76

52

86

62

63

64

65

66

67

68

69

70

71

72

92

95

96

93

94

89

90

91

8887

53

54

55

56

57

58

59

60

61

83

8584

8281

78

79

80

77

49

50

51

74

75

73

Q: Is the check result normal?

YES : 

Go to Step 7.

NO : 

Repair the connector.

STEP 7. Voltage measurement at C-149 PTC 
heater 1 connector.

AC509613AT

Harness side

Connector: C-149 <LHD>

C-149 (GR)

(1) Disconnect the connector, and measure at the 

wiring harness side.

(2) Turn the ignition switch to the "ON" position.

AC509613 CD

Harness side

C-105 (B)

Connector: C-105 <LHD>

35

40

41

42

1817

38

39

15

16

14

3736

12

13

11

32

8

3433

9

10

30

31

7 6

29

5

4

28

3

27

2

26

1

25

19
43

2120

22

23

46

47

4544

24
48

76

52

86

62

63

64

65

66

67

68

69

70

71

72

92

95

96

93

94

89

90

91

8887

53

54

55

56

57

58

59

60

61

83

8584

8281

78

79

80

77

49

50

51

74

75

73

ACA00423

35

40

41

42

1817

38

39

15

16

14

3736

12

13

11

32

8

3433

9

10

30

31

7 6

29

5

4

28

3

27

2

26

1

25

19
43

2120

22

23

46

47

4544

24
48

76

52

86

62

63

64

65

66

67

68

69

70

71

72

92

95

96

93

94

89

90

91

8887

53

54

55

56

57

58

59

60

61

83

8584

8281

78

79

80

77

49

50

51

74

75

73

Connector C-105 
(Harness side)

AE

(3) Disconnect engine-ECU connector C-105 and 

TROUBLESHOOTING

AUTOMATIC AIR CONDITIONER

55B-75

earth terminal 36.

AC310507JD

Connector C-149 
(Harness side)

(4) Voltage between terminal 2 and body earth.

OK: System voltage

Q: Is the check result normal?

YES : 

Go to Step 16.

NO : 

Go to Step 8.

STEP 8. Connector check: A-140X PTC heater 
relay 1 controller connector

AC509815

A-140X

Connector: A-140X

AB

Relay box side

Q: Is the check result normal?

YES : 

Go to Step 9.

NO : 

Repair the connector.

STEP 9. Check the PTC heater relay 1 continuity.
 Refer to .

Q: Is the PTC heater relay 1 in good condition?

YES : 

Go to Step 10.

NO : 

Replace the PTC heater relay 1.

STEP 10. Voltage measurement at A-140X PTC 
heater relay 1 connector.

AC509815

A-140X

Connector: A-140X

AB

Relay box side

(1) Remove the relay, and measure at the relay block 

side.

(2) Turn the ignition switch to the "ON" position.

AC310507

Connector C-140X
(Junction block side)

JX

(3) Voltage between terminal 3 and body earth.

OK: System voltage

Q: Is the check result normal?

YES : 

Go to Step 12.

NO : 

Go to Step 11.

TROUBLESHOOTING

AUTOMATIC AIR CONDITIONER

55B-76

STEP 11. Check the wiring harness between A-
140X PTC heater relay 1 connector terminal No.3 
and the ignition switch (IG2).

AC509815

A-140X

Connector: A-140X

AB

Relay box side

NOTE: 

AC509975AH

Connector: A-28

A-28 (B)

AC509613AW

Connector: C-148 <LHD>

AC509934BW

Connectors: C-207, C-210 <LHD>

Harness side

Junction block (Front view)

C-210

C-207

C-207

C-210

Prior to the wiring harness inspection, check interme-
diate connectors C-148, A-28 and junction block con-
nector C-210,C-207 and repair if necessary.

• Check the PTC heater relay 1 earth supply line 

for open circuit.

Q: Is the check result normal?

YES : 

The trouble can be an intermittent 

malfunction (Refer to GROUP 00, How to 
Cope with Intermittent Malfunction .)

NO : 

Repair the wiring harness.

STEP 12. Voltage measurement at C-140X PTC 
heater relay 1 connector.

AC509815

A-140X

Connector: A-140X

AB

Relay box side

(1) Remove the relay, and measure at the relay block 

side.

AC310507

Connector C-140X
(Junction block side)

JY

(2) Voltage between terminal 2 and body earth.

OK: System voltage

Q: Is the check result normal?

YES : 

Go to Step 14.

NO : 

Go to Step 13.