Mitsubishi 380. Manual — part 195

AUTO A/C DIAGNOSIS

HEATER, AIR CONDITIONING AND VENTILATION

55-76

• 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

.

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

AUTO A/C DIAGNOSIS

HEATER, AIR CONDITIONING AND VENTILATION

55-77

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.

AC305977AJ

CONNECTOR: B-18X

RELAY BOX SIDE

FRONT OF
VEHICLE

JUNCTION BLOCK

TRIANGLE MARK

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

AUTO A/C DIAGNOSIS

HEATER, AIR CONDITIONING AND VENTILATION

55-78

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.

25DB148A

B-20

CONNECTOR: B-20

AC305218

B-28 (B)

HARNESS SIDE

AB

CONNECTOR: B-28 <3.8 L>

AUTO A/C DIAGNOSIS

HEATER, AIR CONDITIONING AND VENTILATION

55-79

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.

AC305218

B-28 (B)

HARNESS SIDE

AB

CONNECTOR: B-28 <3.8 L>

25DB149A

CONNECTOR

B-20

25DB148A

B-20

CONNECTOR: B-20

AC209365

CONNECTOR B-28
(HARNESS SIDE)

GS