2005 MITSUBISHI LANCER Workshop Manual

TROUBLESHOOTING
HEATER, AIR CONDITIONER AND VENTILATION55-21
COMMENTS ON TROUBLE SYMPTOM
If cool air is not distributed when the A/C switch is on,
the air thermo sensor or the A/C compressor relay
system may be defective.
TROUBLESHOOTING HINTS
•Improper amount of refrigerant
•Malfunction of the air thermo sensor
•Malfunction of the dual pressure switch
•Malfunction of the A/C compressor relay
•Malfunction of the A/C refrigerant temperature
switch
•Malfunction of the magnetic clutch
•Malfunction of the manual air conditioner control
panel (A/C-ECU)
•Damaged the wiring harness or connectors
•Malfunction of the engine-ECU or the
engine-A/T-ECU
DIAGNOSIS
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.55-56 ."
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 "Blower fan
and motor do not turn P.55-29."
STEP 3. Check the A/C compressor.
Check the A/C compressor for compressor oil leaks.
Q: Is the check result satisfactory?
YES :
Go to Step 4.
NO : Replace the A/C compressor or the
expansion valve.
STEP 4. Connector check: B-114 A/C compressor
connector and C-123 engine-ECU connector
or C-122 engine-A/T-ECU connector
Q: Is the check result normal?
YES :
Go to Step 5.
NO : Repair the connector.
AC303786
Connector: B-114
<4G1-R.H.D.>
AB
Harness side
B-114 (B)
AC303794
Connector: B-114
<4G6-R.H.D.>
AB
Harness side
B-114 (B)
AC303817
Connectors: C-122 , C-123
AF

C-122C-122 (GR)
C-123 (Y)
C-123 Harness side

TROUBLESHOOTING
HEATER, AIR CONDITIONER AND VENTILATION55-22
STEP 5. Voltage measurement at the B-114 A/C
compressor connector.
(1) Disconnect the connector, and measure at the
wiring harness side.
(2) Turn the ignition switch to the "ON" position.(3) Disconnect engine-ECU connector C-123, and
earth terminal 8.
(4) Disconnect engine-A/T-ECU connector C-122,
and earth terminal 20.
(5) Measure the voltage between terminal 1 and
body earth.
OK: System voltage
Q: Is the check result normal?
YES :
Go to Step 6.
NO : Refer to Inspection procedure 11 "A/C
compressor power supply system P.55-59."
AC303786
Connector: B-114
<4G1-R.H.D.>
AB
Harness side
B-114 (B)
AC303794
Connector: B-114
<4G6-R.H.D.>
AB
Harness side
B-114 (B)
AC303817
Connectors: C-122 , C-123
AF

C-122C-122 (GR)
C-123 (Y)
C-123 Harness side
AC305159 Connector C-123
(Harness side)AB
AC305161
Connector C-122
(Harness side)
AB
AC301541EW
Connector B-114
(Harness side)
1

TROUBLESHOOTING
HEATER, AIR CONDITIONER AND VENTILATION55-23
STEP 6. Connector check: C-139 A/C-ECU
connector
Q: Is the check result normal?
YES :
Go to Step 7.
NO : Repair the connector.
STEP 7. Voltage measurement at C-139 A/C-ECU
connector.
(1) Disconnect the connector, and measure at the
wiring harness side.
(2) Turn the ignition switch to the "ON" position.
(3) Turn the blower switch to the "ON" position.
(4) Measure the voltage between terminal 8 and
body earth.
OK: System voltage
Q: Is the check result normal?
YES :
Go to Step 10.
NO : Go to Step 8.
STEP 8. Connector check: C-109 resistor
connector
Q: Is the check result normal?
YES :
Go to Step 9.
NO : Repair the connector.
STEP 9. Check the wiring harness between C-109
resistor connector terminal No.4 and C-139
A/C-ECU connector terminal No.8.
Q: Is the check result normal?
YES :
The trouble can be an intermittent
malfunction (Refer to GROUP 00, How to
Cope with Intermittent Malfunction P.00-5).
NO : Repair the wiring harness.
AC303818
Connector: C-139

AJ
Harness side
C-139 (B)
11 12657 8 9 103 421
AC303818
Connector: C-139

AJ
Harness side
C-139 (B)
11 12657 8 9 103 421
AC301541EY
Connector C-139
(Harness side)
11 12
65
7 8 9 10
3 421
AC303816
Connector: C-109
AJ

Harness side
AC303816
Connector: C-109
AJ

Harness side
AC303818
Connector: C-139

AJ
Harness side
C-139 (B)
11 12657 8 9 103 421

TROUBLESHOOTING
HEATER, AIR CONDITIONER AND VENTILATION55-24
STEP 10. Connector check: A-31 dual pressure
switch connector
Q: Is the check result normal?
YES :
Go to Step 11.
NO : Repair the connector.
STEP 11. Check the dual pressure switch
operation.
Refer to P.55-69.
Q: Is the dual pressure switch operating properly?
YES :
Go to Step 12.
NO : Replace the dual pressure switch.
STEP 12. Connector check: C-106 air thermo
sensor connector
Q: Is the check result normal?
YES :
Go to Step 13.
NO : Repair the connector.
STEP 13. Check the wiring harness between
C-106 air thermo sensor connector (terminals 4
and 5) and C-139 A/C-ECU connector (terminals 4
and 6).
•Check the air thermo sensor output and earth line
for open or short circuit.
Q: Is the check result normal?
YES :
Go to Step 14.
NO : Repair the wiring harness.
AC303825
Connector: A-31

AH
A-31 (BR)
Harness side
AC303816
Connector: C-106
AH

AC303816
Connector: C-106
AH

AC303818
Connector: C-139

AJ
Harness side
C-139 (B)
11 12657 8 9 103 421

TROUBLESHOOTING
HEATER, AIR CONDITIONER AND VENTILATION55-25
STEP 14. Check the wiring harness between A-31
dual pressure switch connector terminal No.1
and C-139 A/C-ECU connector terminal No.1.
NOTE:
Prior to the wiring harness inspection, check
intermediate connector C-28, and repair if necessary.
•Check the dual pressure switch output line for
open or short circuit.
Q: Is the check result normal?
YES :
Go to Step 15.
NO : Repair the wiring harness.
STEP 15. Connector check: C-125 engine-ECU
connector or C-126 engine-A/T-ECU
connector
Q: Is the check result normal?
YES :
Go to Step 16.
NO : Repair the connector.
AC303825
Connector: A-31

AH
A-31 (BR)
Harness side
AC303818
Connector: C-139

AJ
Harness side
C-139 (B)
11 12657 8 9 103 421
AC303814
Connector: C-28

AJ
AC303817
Connectors: C-125 , C-126
AH

C-126 (GR)
C-125Harness side
C-125 (Y)
C-126
38
46
45 44 43 42 41 40 3937 36 35 34 33 32 3177 76 75 74 73 72 71
78 79 80 81 82 83 84 85 86 87 88 89
90 98 97 96 95 94 93 92 91

TROUBLESHOOTING
HEATER, AIR CONDITIONER AND VENTILATION55-26
STEP 16. Check the wiring harness between
C-125 engine-ECU connector terminal
No.45 or C-126 engine-A/T-ECU connector
terminal No.83 and A-31 dual pressure switch
connector terminal No.2.NOTE:
Prior to the wiring harness inspection, check
intermediate connector C-28 and C-135, and repair if
necessary.
•Check the communication line for open or short
circuit.
Q: Is the check result normal?
YES :
Go to Step 17.
NO : Repair the wiring harness.
AC303825
Connector: A-31

AH
A-31 (BR)
Harness side
AC303817
Connectors: C-125 , C-126
AH

C-126 (GR)
C-125Harness side
C-125 (Y)
C-126
38
46
45 44 43 42 41 40 3937 36 35 34 33 32 3177 76 75 74 73 72 71
78 79 80 81 82 83 84 85 86 87 88 89
90 98 97 96 95 94 93 92 91
AC303814
Connector: C-28

AJ
AC303818
Connector: C-135

AH
C-135 (L)

TROUBLESHOOTING
HEATER, AIR CONDITIONER AND VENTILATION55-27
STEP 17. Connector check: C-123 engine-ECU
connector or C-124 engine-A/T-ECU
connector
Q: Is the check result normal?
YES :
Go to Step 18.
NO : Repair the connector.
STEP 18. Check the wiring harness between
C-123 engine-ECU connectors terminal No.24
or C-124 engine-A/T-ECU connectors
terminal No.61 and C-139 A/C-ECU
connector terminal No.2.
•Check the communication line for open or short
circuit.
Q: Is the check result normal?
YES :
Go to Step 19.
NO : Repair the wiring harness.
AC303817
Connectors: C-123 , C-124
AG

C-123 (Y)
C-123Harness side
C-124 (GR)
46 45 44 43 42 41
57 56 55 54 53 52 515049 48 47
66 65 64 63 62 61 60 59 58
C-124
AC303817
Connectors: C-123 , C-124
AG

C-123 (Y)
C-123Harness side
C-124 (GR)
46 45 44 43 42 41
57 56 55 54 53 52 515049 48 47
66 65 64 63 62 61 60 59 58
C-124
AC303818
Connector: C-139

AJ
Harness side
C-139 (B)
11 12657 8 9 103 421

TROUBLESHOOTING
HEATER, AIR CONDITIONER AND VENTILATION55-28
STEP 19. Check the magnetic clutch operation.
Refer to P.55-93.
Q: Can the sound of the magnetic clutch (click) be
heard?
YES :
Go to Step 20.
NO : Replace the compressor magnet clutch.
STEP 20. Check the refrigerant temperature
switch.
Refer to P.55-95.
Q: Is the refrigerant temperature switch operating
properly?
YES :
Go to Step 21.
NO : Replace the refrigerant temperature switch.
STEP 21. Check the air thermo sensor.
Refer to P.55-90.
Q: Is the air thermo sensor in good condition?
YES :
Go to Step 22.
NO : Replace the air thermo sensor.
STEP 22. Check the refrigerant level.
Refer to P.55-69.
Q: Is the refrigerant level correct?
YES :
Go to Step 23.
NO : Correct the refrigerant level (Refer to
On-vehicle Service P.55-70).
STEP 23. Replace the A/C-ECU.
Check that the air conditioner works normally.
Q: Is the check result normal?
YES :
This diagnosis is complete.
NO : Replace the engine-ECU or the
engine-A/T-ECU .