Mitsubishi Colt Ralliart. Manual - part 748

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI) <4G1>

13B-317

Inspection Procedure 24: A/C Compressor Relay System

OPERATION

• The battery voltage is applied to the A/C com-

pressor relay (terminal No. 1 and No. 3).

• The engine-ECU (terminal No. 110) makes the 

power transistor in the unit be in ON position and 
makes currents go on the A/C compressor relay 
coil, and that makes the relay be in ON position.

• When the A/C compressor relay is switched ON, 

the battery voltage is supplied from the A/C com-
pressor relay (terminal No. 4) to the A/C com-
pressor (terminal No. 1).

1

AK402705

3

1

2

4

R

92 93 94 95969798

77 78 79 808182838485868788899091

99

100

107 108 109 110 111112113114115116117118119120121
122 123 124 125126127128129130131132133134135136

101102103104105106

71 72

73 74

75 76

24

6

10A

L

B-R

B-R

Fusible link

B-108

J/B

A/C 
compressor 
relay

B-104

1

A-130

MU802653

A/C refrigerant 
temperature 
switch

A/C compressor assembly

Magnetic 
clutch

A/C Compressor Relay Circuit

110

Wire colour code
B: Black  LG: Light green  G: Green   L: Blue   W: White   Y: Yellow   SB: Sky blue   BR: Brown    O: Orange   GR: Gray
R: Red   P: Pink   V: Violet  P: Purple

AF

A-08

Engine-ECU

2

B-112

4

A-17

8

B-110

G

6

1 

3

4

2

Main

Index

Group

TOC

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI) <4G1>

13B-318

FUNCTION

• When the A/C switch ON signal is input to the 

engine-ECU, the engine-ECU places the A/C 
compressor relay in the ON position. Accordingly, 
the battery voltage supplied to the A/C compres-
sor operates the magnet clutch.

PROBABLE CAUSES

• Failed A/C compressor relay

• Failed A/C compressor

• Open/short circuit in or damage to the A/C com-

pressor relay circuit or loose connector contact

• Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. Connector check: B-104 A/C compressor 
relay connector

Q: Is the check result normal?

YES : 

Go to Step 2 .

NO : 

Repair or replace.

STEP 2. Check A/C compressor relay.

• Check A/C compressor relay (Refer to GROUP 

55A 

− On-vehicle Service − Power Relay Check 

P.55A-52

).

Q: Is the check result normal?

YES : 

Go to Step 3 .

NO : 

Replace A/C compressor relay.

STEP 3. Perform voltage measurement at B-104 
A/C compressor relay.

•

Disconnect connector and measure at harness side.

• Voltage between terminal No. 1, No. 3 and earth.

OK: System voltage

Q: Is the check result normal?

YES : 

Go to Step 4 .

NO : 

Check intermediate connector B-108, and 

repair if necessary. If intermediate 
connector is normal, check and repair 
harness between battery and B-104 
(terminal No. 1 and No. 3) A/C compressor 
relay connector.

• Check power supply line for 

open/short circuit.

3

2

1

4

AK402116

J/B side 
connector

Connector: B-104
J/B (front side)

B-104

AC

3

2

1

4

AK402116

J/B side 
connector

Connector: B-104
J/B (front side)

B-104

AC

Main

Index

Group

TOC

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI) <4G1>

13B-319

STEP 4. Check harness between battery and 
B-104 (terminal No. 1 and No. 3) A/C compressor 
relay connector.

NOTE: Before checking harness, check intermediate 
connector B-108 and repair if necessary.

• Check power supply line for damage.

Q: Is the check result normal?

YES : 

Go to Step 5 .

NO : 

Repair.

STEP 5. Connector check: A-08 engine-ECU 
connector

Q: Is the check result normal?

YES : 

Go to Step 6 .

NO : 

Repair or replace.

3

2

1

4

AK402116

J/B side 
connector

Connector: B-104
J/B (front side)

B-104

AC

AK402725

77

78

79

80

81

82

83

84

92

93

94

95

96

97

98

99

85

86

87

88

89

90

91

100

101

102

103

104

105

106

115

116

117

118

119

120

121

107

108

109

110

111

112

113

114

130

131

132

133

134

135

136

122

123

124

125

126

127

128

129

72 71

74 73

76 75

R

AI

A-08

Connector: 

A-08

A-08 Special tool power plant ECU check 
harness

Engine-ECU

Battery

Main

Index

Group

TOC

TROUBLESHOOTING

MULTIPORT FUEL INJECTION (MPI) <4G1>

13B-320

STEP 6. Perform voltage measurement at A-08 
engine-ECU connector.

•

Disconnect connector and measure at harness side.

• Voltage between terminal No. 110 and earth.

OK: System voltage

Q: Is the check result normal?

YES : 

Go to Step 7 .

NO : 

Check intermediate connector B-110, and 

repair if necessary. If intermediate 
connector is normal, check and repair 
harness between B-104 (terminal No. 2) 
A/C compressor relay connector and A-08 
(terminal No. 110) engine-ECU connector.

• Check signal line for open/short 

circuit.

AK402725

77

78

79

80

81

82

83

84

92

93

94

95

96

97

98

99

85

86

87

88

89

90

91

100

101

102

103

104

105

106

115

116

117

118

119

120

121

107

108

109

110

111

112

113

114

130

131

132

133

134

135

136

122

123

124

125

126

127

128

129

72 71

74 73

76 75

R

AI

A-08

Connector: 

A-08

A-08 Special tool power plant ECU check 
harness

Engine-ECU

Battery

3

2

1

4

AK402116

J/B side 
connector

Connector: B-104
J/B (front side)

B-104

AC

Main

Index

Group

TOC