2005 MITSUBISHI 380 Workshop Manual

AUTO A/C DIAGNOSIS
HEATER, AIR CONDITIONING AND VENTILATION55-76
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.55-122."
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.55-89."
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. Using scan tool , read the A/C diagnostic trouble
code.
Check if an A/C-ECU DTC is set.
(1) Connect scan tool 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 : Go to Step 5.
NO : Refer to DIAGNOSTIC TROUBLE CODE CHART
P.55-9.

AUTO A/C DIAGNOSIS
HEATER, AIR CONDITIONING AND VENTILATION55-77
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.
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
VOLTAGETESTER
CONNECTIONSPECIFIED
CONDITION
Not applied 1
4 Open circuit
Connect
terminal 2 to the
positive battery
terminal
Connect
terminal 3 to the
negative battery
terminal1
4 Less than 2 ohms

AUTO A/C DIAGNOSIS
HEATER, AIR CONDITIONING AND VENTILATION55-78
STEP 7. Check Engine ECU connector B-20 and A/C
compressor assembly B-28 for loose, corroded or
damaged terminals, or terminals pushed back in the
connector.
Q: Are Engine ECU connector B-20 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.

AUTO A/C DIAGNOSIS
HEATER, AIR CONDITIONING AND VENTILATION55-79
STEP 8. Measure the voltage at A/C compressor assembly
connector B-28.
(1) Disconnect A/C compressor assembly connector B-28 and
measure the voltage at the relay box side.
(2) Disconnect powertrain control module connector B-20 and
ground harness side terminal No.6.
(3) Turn the ignition switch to the "ON" position.
(4) A/C compressor assembly connector B-28 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 15.
NO : Go to Step 9.

AUTO A/C DIAGNOSIS
HEATER, AIR CONDITIONING AND VENTILATION55-80
STEP 9. Measure the voltage at A/C compressor clutch
relay connector B-18X.
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 relay box side.
(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal 2 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 11.
NO : Go to Step 10.
STEP 10. Check the wiring harness between A/C
compressor clutch relay connector B-18X (terminal 2) and
the ignition switch (IG2).

AUTO A/C DIAGNOSIS
HEATER, AIR CONDITIONING AND VENTILATION55-81
NOTE: Also check intermediate connector A-13, junction block
connectors C-214 and C-215 for loose, corroded, or damaged
terminals, or terminals pushed back in the connector. If inter-
mediate connector A-13, junction block connector C-214 or
C-215 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 2) and the ignition
switch (IG2) 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.

AUTO A/C DIAGNOSIS
HEATER, AIR CONDITIONING AND VENTILATION55-82
STEP 11. Measure the voltage at A/C compressor clutch
relay connector B-18X.
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.

AUTO A/C DIAGNOSIS
HEATER, AIR CONDITIONING AND VENTILATION55-83
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.