Mitsubishi Evolution X. Manual — part 1282
AUTO A/C DIAGNOSIS
TSB Revision
HEATER, AIR CONDITIONING AND VENTILATION
55-79
.
FUNCTION
Compressor that recovers the refrigerant, which evaporated in
the evaporator and became a high-temperature and high-pres-
sure gas, and turns it into liquid again.
.
PROBABLE CAUSES
• Insufficient refrigerant
• Malfunction of connector.
• Malfunction of the harness (A/C compressor circuit is
open/shorted to ground)
• Malfunction of the A/C pressure sensor.
• Malfunction of the A/C compressor.
• Malfunction of the A/C compressor clutch relay.
• Malfunction of the A/C-ECU.
DIAGNOSIS
Required Special Tools:
• MB991223: Harness Set
• MB992006: Extra Fine Probe
• MB991658: Test Harness Set
• MB991958: Scan Tool (M.U.T.-III Sub Assembly)
• MB991824: V.C.I.
• MB991827: M.U.T.-III USB Cable
• MB991910: M.U.T.-III Main Harness A
AC709111
Connector: A-17X
AB
AC709137
Connector: B-10
AB
C-10 (GR)
AC709136
Connector: B-110
AB
C-110 (GR)
AUTO A/C DIAGNOSIS
TSB Revision
HEATER, AIR CONDITIONING AND VENTILATION
55-80
STEP 1. Using scan tool MB991958, diagnose the CAN bus
line.
CAUTION
To prevent damage to scan tool MB991958, always turn the
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991958.
(1) Connect scan tool MB991958. Refer to "How to connect the
Scan Tool (M.U.T.-III)
(2) Turn the ignition switch to the "ON" position.
(3) Diagnose the CAN bus line.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the CAN bus line found to be normal?
YES : Go to Step 2.
NO : Repair the CAN bus lines (Refer to GROUP 54C,
precautions on how to repair the CAN bus lines
).
STEP 2. 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 DTC set?
YES : Refer to Diagnostic Trouble Code Chart
.
NO : Go to Step 3.
STEP 3. Check A/C compressor assembly connector B-110
for loose, corroded or damaged terminals, or terminals
pushed back in the connector.
Q: Is A/C compressor assembly connector B-110 in good
condition?
YES : Go to Step 4.
NO : Repair or replace the connector. Refer to GROUP
00E, Harness Connector Inspection
AC608435
Data link connector
MB991827
MB991824
MB991910
AB
AUTO A/C DIAGNOSIS
TSB Revision
HEATER, AIR CONDITIONING AND VENTILATION
55-81
STEP 4. Check the A/C compressor clutch operation.
Connect the compressor connector terminal to the battery posi-
tive (+) terminal and ground the battery’s negative (-) terminal
to the compressor unit. At that time, the A/C compressor clutch
should make a definite operating sound.
Q: Can the sound (click) of the A/C compressor clutch
operation be heard?
YES : Go to Step 5.
NO : Replace the compressor magnet clutch.
STEP 5. Check A/C compressor clutch relay connector
A-17X for loose, corroded or damaged terminals, or
terminals pushed back in the connector.
Q: Is A/C compressor clutch relay connector A-17X in good
condition?
YES : Go to Step 6.
NO : Repair or replace the connector. Refer to GROUP
00E, Harness Connector Inspection
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.
AC506471
Battery voltage
Tester connection Specified
condition
Not applied
3
− 4
Open circuit
• Connect
terminal 2 to the
positive battery
terminal
• Connect
terminal 1 to the
negative battery
terminal
3
− 4
Less than 2 ohms
AC605626
AC609971
AB
4
1
2
3
3
1
4
2
A/C compressor clutch relay
AUTO A/C DIAGNOSIS
TSB Revision
HEATER, AIR CONDITIONING AND VENTILATION
55-82
STEP 7. Check engine control module connector B-10 for
loose, corroded or damaged terminals, or terminals
pushed back in the connector.
Q: Is engine control module connector B-10 in good
condition?
YES : Go to Step 8.
NO : Repair or replace the connector. Refer to GROUP
00E, Harness Connector Inspection
STEP 8. Measure the voltage at A/C compressor assembly
connector B-10.
(1) Disconnect A/C compressor assembly connector B-10 and
measure the voltage at the wiring harness side.
(2) Disconnect engine control module connector B-10 and
ground harness side terminal No.102.
(3) Turn the ignition switch to the "ON" position.
(4) A/C compressor assembly connector B-110 terminal 1 and
ground.
• The measured value should be approximately 12 volts
(battery positive voltage).
Q: Is the measured voltage approximately 12 volts?
YES : Go to Step 13.
NO : Go to Step 9.
STEP 9. Measure the voltage at A/C compressor clutch
relay connector A-17X.
(1) Disconnect A/C compressor connector A-17X and measure
the voltage at the relay box side.
(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal 4 and ground.
• The measured value should be approximately 12 volts
(battery positive voltage).
(4) Measure the voltage between terminal 2 and ground.
• The measured value should be approximately 12 volts
(battery positive voltage).
Q: Is the measured voltage approximately 12 volts?
YES : Go to Step 11.
NO : Go to Step 10.
AC608254 CM
Connector B-110
(Harness side)
AC608254 CN
Connector A-17X
(Harness side)
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