Mitsubishi Galant 9G. Manual - part 280

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-196

STEP 11. Measure the voltage at A/C compressor clutch 
relay connector B-18X. 

CAUTION

The top and bottom of the A/C compressor connector are 
difficult to identify. Prior to inspection, confirm the triangle 
mark on the relay box.
(1) Disconnect A/C compressor connector B-18X and measure 

the voltage at the wiring harness side.

(2) Measure the voltage between terminal 1 and ground.

• The measured value should be approximately 12 volts 

(battery positive voltage).

Q: Is the measured voltage approx. 12 volts?

YES :  Go to Step 13.
NO :   Go to Step 12.

STEP 12. Check the wiring harness between A/C 
compressor clutch relay connector B-18X (terminal 1) and 
the battery.

AC305977AJ

CONNECTOR: B-18X

RELAY BOX SIDE

FRONT OF 
VEHICLE

JUNCTION BLOCK 
TRIANGLE MARK

AC209365GU

CONNECTOR B-18X 
(RELAY BOX SIDE)

AC305977AJ

CONNECTOR: B-18X

RELAY BOX SIDE

FRONT OF 
VEHICLE

JUNCTION BLOCK 
TRIANGLE MARK

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-197

NOTE: Also check intermediate connector A-13 for loose, cor-
roded, or damaged terminals, or terminals pushed back in the 
connector. If intermediate connector A-13 is damaged, repair or 
replace the connector as described in GROUP 00E, Harness 
Connector Inspection 

P.00E-2

.

Q: Is the wiring harness between A/C compressor clutch 

relay connector B-18X (terminal 1) and the battery in 
good condition?
YES : It can be assumed that this malfunction is intermittent. 

Refer to GROUP 00, How to Use 
Troubleshooting/Inspection Service Points 

− How to 

Cope with Intermittent Malfunctions 

P.00-14

.

NO :  Repair the wiring harness. Check that the air 

conditioning works normally.

STEP 13. Check the wiring harness between A/C 
compressor clutch relay connector B-18X (terminal 4) and 
A/C compressor assembly connector B-28 (terminal 1).
Q: Is the wiring harness between A/C compressor clutch 

relay connector B-18X (terminal 4) and A/C compressor 
connector B-28 (terminal 1) in good condition?
YES : Go to Step 14.
NO :  Repair the wiring harness. Check that the air 

conditioning works normally.

AC305210

A-13 (GR)

AR

CONNECTOR: A-13

AC305977AJ

CONNECTOR: B-18X

RELAY BOX SIDE

FRONT OF 
VEHICLE

JUNCTION BLOCK 
TRIANGLE MARK

AC305214

B-28 (B)

HARNESS SIDE

AD

CONNECTOR: B-28 <2.4L>

AC305218

B-28 (B)

HARNESS SIDE

AB

CONNECTOR: B-28 <3.8 L>

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-198

STEP 14. Check the wiring harness between powertrain 
control module connector B-21 (terminal 81) and A/C 
compressor clutch relay connector B-18X (terminal 3).
Q: Is the wiring harness between powertrain control 

module connector B-21 (terminal 81) and A/C 
compressor clutch relay connector B-18X (terminal 3) in 
good condition?
YES : It can be assumed that this malfunction is intermittent. 

Refer to GROUP 00, How to Use 
Troubleshooting/Inspection Service Points 

− How to 

Cope with Intermittent Malfunctions 

P.00-14

.

NO :  Repair the wiring harness. Check that the air 

conditioning works normally.

STEP 15. Check A/C-ECU connector C-15 for loose, 
corroded or damaged terminals, or terminals pushed back 
in the connector.
Q:  Is A/C-ECU connector C-15 in good condition?

YES : Go to Step 16.
NO :  Repair or replace the connector. Refer to GROUP 

00E, Harness Connector Inspection 

P.00E-2

. Check 

that the air conditioning works normally.

AC305977AJ

CONNECTOR: B-18X

RELAY BOX SIDE

FRONT OF 
VEHICLE

JUNCTION BLOCK 
TRIANGLE MARK

AC305216

B-21 (B)

AC

CONNECTOR: B-21 <2.4L>

HARNESS SIDE

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

AC305229

B-21 (B)

AB

HARNESS SIDE

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

CONNECTOR: B-21 <3.8 L>

AC305233

CONNECTOR: C-15

BG

C-105 (B)

HARNESS SIDE

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-199

STEP 16. Measure the voltage at A/C-ECU connector C-15. 
(1) Disconnect A/C-ECU connector C-15 and measure the 

voltage at the relay box side.

(2) Disconnect powertrain control module connector B-21 and 

ground harness side terminal No.81.

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

AC305233

CONNECTOR: C-15

BG

C-105 (B)

HARNESS SIDE

AC305216

B-21 (B)

AC

CONNECTOR: B-21 <2.4L>

HARNESS SIDE

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

AC305229

B-21 (B)

AB

HARNESS SIDE

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

CONNECTOR: B-21 <3.8 L>

AC306468

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

AC306468

CONNECTOR B-21 
(HARNESS SIDE)

AD