Mitsubishi Galant 9G. Manual — part 261

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-120

.

TECHNICAL DESCRIPTION (COMMENT)

If cool air is not distributed when the A/C switch is on,
the A/C compressor clutch relay system may be
defective.

.

TROUBLESHOOTING HINTS

• Improper amount of refrigerant

• Malfunction of the air thermo sensor

• Malfunction of the ambient air temperature sen-

sor

• Malfunction of the A/C pressure sensor

• Malfunction of the A/C compressor clutch relay

• Malfunction of the A/C refrigerant temperature

switch

• Malfunction of the air conditioning compressor

clutch

• Malfunction of the A/C-ECU

• Malfunction of the PCM

• Damaged harness wires or connectors

DIAGNOSIS

Required Special Tools:

• MB991223: Harness Set

• MB991958: Scan Tool (MUT-III Sub Assembly)

• MB991824: Vehicle Communication Interface (V.C.I.)

• MB991827: MUT-III USB Cable

• MB991910: MUT-III Main Harness A (Vehicles with CAN

communication system)

STEP 1. Check the defogger and outside/inside air
selection damper control motor operation.
Q: Do the defogger and outside/inside air selection damper

control motor work normally?
YES : Go to Step 2.
NO : Refer to Inspection procedure 10, "Malfunction of the

A/C-ECU power supply system

P.55A-170

."

STEP 2. Check the blower motor operation.
Q: Does the blower motor work normally?

YES : Go to Step 3.
NO : Refer to Inspection procedure 5, "Front blower fan

and motor do not turn

P.55A-137

."

STEP 3. Check the A/C compressor.
Check the A/C compressor for compressor oil leaks.
Q: Is the check result satisfactory?

YES : Replace the A/C compressor or the expansion valve.
NO : Go to Step 4.

AC305415

CONNECTORS: C-214, C-215

JUNCTION BLOCK
(FRONT VIEW)

C-215

C-214

BB

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-121

STEP 4. Using scan tool MB991958, read the diagnostic
trouble code.
Check if an A/C-ECU DTC is set.
(1) Connect scan tool MB991958 to the data link connector.
(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 check result satisfactory?

YES : Refer to DIAGNOSTIC TROUBLE CODE CHART

P.55A-10

.

NO : Go to Step 5.

STEP 5. Check A/C compressor clutch relay connector
B-18X for loose, corroded or damaged terminals, or
terminals pushed back in the connector.
Q: Is A/C compressor clutch relay connector B-18X in

good condition?
YES : Go to Step 6.
NO : Repair or replace the connector. Refer to GROUP

00E, Harness Connector Inspection

P.00E-2

. Check

that the air conditioning works normally.

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

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-122

STEP 6. Check the A/C compressor clutch relay continuity.
Follow the table below to check the A/C compressor clutch
relay for continuity.

Q: Is the A/C compressor clutch relay in good condition?

YES : Go to Step 7.
NO : Replace the A/C compressor clutch relay. Check that

the air conditioning works normally.

BATTERY
VOLTAGE

TESTER
CONNECTION

SPECIFIED
CONDITION

Not applied

1

− 4

Open circuit

• Connect

terminal 2 to the
positive battery
terminal

• Connect

terminal 3 to the
negative battery
terminal

1

− 4

Less than 2 ohms

AC306655

2

1

3

4

1

2

4

3

AB

A/C COMPRESSOR CLUTCH RELAY

FRONT OF
VEHICLE

JUNCTION BLOCK
TRIANGLE MARK

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-123

STEP 7. Check powertrain control module connector B-21
and A/C compressor assembly B-28 for loose, corroded or
damaged terminals, or terminals pushed back in the
connector.
Q: Are powertrain control module connector B-21 and A/C

compressor assembly B-28 in good condition?
YES : Go to Step 8.
NO : Repair or replace the connector. Refer to GROUP

00E, Harness Connector Inspection

P.00E-2

. Check

that the air conditioning works normally.

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>

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>