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Mitsubishi Galant 9G. Manual - part 281

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-200

(4) Measure the voltage between A/C-ECU connector C-15

terminal No.10 and ground.

• The measured value should be approximately 12 volts

(battery positive voltage).

Q: Does the measured voltage correspond with this range?

YES : Go to Step 18.
NO : Go to Step 17.

STEP 17. Check the wiring harness between A/C
compressor clutch relay connector B-18X (terminal 4) and
A/C-ECU connector C-15 (terminal 10).

AC209365HI

CONNECTOR C-15
(HARNESS SIDE)

AC305977AJ

CONNECTOR: B-18X

RELAY BOX SIDE

FRONT OF
VEHICLE

JUNCTION BLOCK
TRIANGLE MARK

AC305234

C-15 (B)

C-23

C-15

HARNESS SIDE

C-23

CONNECTORS: C-15, C-23

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-201

NOTE: Also check intermediate connectors A-13 and C-23 for
loose, corroded, or damaged terminals, or terminals pushed
back in the connector. If intermediate connector A-13 or C-23 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 4) and A/C-ECU
connector C-15 (terminal 10) 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 18. Check the refrigerant temperature switch.

CAUTION

Do not heat more than necessary.
(1) Dip the metal part of the cooling temperature switch into

engine oil and increase the oil temperature using a gas
burner or similar.

(2) When the oil temperature reaches the standard value,

check that voltage is supplied between the terminals.

Standard value:

NOTE: When the oil temperature is 155

C (311

F) or more

and there is no continuity, the resistance will not be 2

Ω

lower until the oil temperature reduces to 125

C (257

F) or

less.

Q: Is the refrigerant temperature switch operating

properly?
YES : Go to Step 19.
NO : Replace the refrigerant temperature switch. Check

that the air conditioning works normally.

AC305210

A-13 (GR)

CONNECTOR: A-13

ITEM

TEMPERATURE

Less than 2 ohms Slightly below 155

°C (311°F)

No continuity

155

°C (311°F) or more

AC100787

THERMOMETER

ENGINE OIL

AC100810

LESS THAN 2

Ω

NO CONTINUITY

125˚C
(257˚F)

155˚C
(311˚F)

OIL TEMPRATURE

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-202

STEP 19. Check the air conditioning 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 air conditioning com-
pressor clutch should make a definite operating sound.
Q: Can the sound (click) of the air conditioning

compressor clutch operation be heard?
YES : Go to Step 20.
NO : Replace the compressor magnet clutch. Check that

the air conditioning works normally.

STEP 20. Check the air thermo sensor.
Measure the resistance between connector terminals 1 and 2
under at least two different temperatures. The resistance val-
ues should generally match those in the graph.
NOTE: The temperature at the check should not exceed the
range in the graph.
Q: Is the air thermo sensor in good condition?

YES : Go to Step 21.
NO : Replace the air thermo sensor. Check that the air

conditioning works normally.

STEP 21. Check the ambient air temperature sensor.
Measure the resistance between the sensor terminals under at
least two temperatures. The resistance values should meet the
values shown.
NOTE: The temperature should be within the shown range.
Q: Is the ambient air temperature sensor in good

condition?
YES : Go to Step 22.
NO : Replace the ambient air temperature sensor. Check

that the air conditioning works normally.

AC206292AB

A/C COMPRESSOR
CLUTCH
CONNECTOR

AC001043

RESISTANCE k

Ω

-10

TEMPERATURE ˚C(˚F)

(14)

(32)

(50)

(86)

(104)

(68)

AC209942AB

REGISTANCE
k

Ω

(32) (68)

TEMPERATURE ˚C (˚F)

(104)

(140)

-20

(-4)

-30

(-22)

MANUAL A/C DIAGNOSIS

TSB Revision

HEATER, AIR CONDITIONING AND VENTILATION

55A-203

STEP 22. Check the A/C pressure sensor operation.
(1) Assemble a gauge manifold on the high pressure service

valve.

(2) Disconnect the A/C pressure sensor connector and connect

special tool test harness MB991658 as shown in the
illustration.

(3) Turn ON the engine and then turn ON the air conditioner

switch.

(4) At this time, check to see that the voltage of A/C pressure

sensor terminal No. 2 reflects the specifications of the
figure.
NOTE: The allowance shall be defined as

5%.

Q: Is the A/C pressure sensor operating properly?

YES : Go to Step 23.
NO : Replace the A/C pressure sensor. Check that the air

conditioning works normally.

STEP 23. Check the refrigerant level.
Use the refrigerant recovery station to remove all of the refrig-
erant, and then calculate the amount of the refrigerant and
charge it.
Q: Is the refrigerant level correct?

YES : Go to Step 24.
NO : Correct the refrigerant level (Refer to On-vehicle

Service

P.55A-262

). Check that the air conditioning

works normally.

STEP 24. Replace the A/C-ECU.
Q: Does the A/C operate normally?

YES : The procedure is complete.
NO : Replace the powertrain control module. Check that

the air conditioning works normally.

AC305034

A/C PRESSURE SENSOR

AC307368

A/C
PRESSURE
SENSOR
SIDE

MB991658

HARNESS SIDE

AC208297AB

REFRIGERANT PRESSURE (MPa)

OUTPUT VOLTAGE

(V)

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