Mitsubishi Grandis. Manual - part 303

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55-97

Step 25. Check the wiring harness between C-207 
PTC heater relay 2 connector terminal No.4 and 
the fusible link (28).

NOTE: 

Prior to the wiring harness inspection, check 
intermediate connector C-124, and repair if 
necessary.

• Check the PTC heater relay 2 power supply line 

for open circuit.

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.

Step 26. Check the wiring harness between C-207 
PTC heater relay 2 connector terminal No.1 and 
C-105 A/C-ECU connector terminal No.46.

NOTE: Prior to the wiring harness inspection, check 
joint connector C-01, and repair if necessary.

• Check the PTC heater relay 2 earth line for open 

or short circuit.

Q: Is the check result normal?

YES : 

 Go to Step 27.

NO : 

Repair the wiring harness.

AC310623

Connector: C-207 <LHD>

AF

3

4

5

1

2

Junction block side

Junction block (Front view)

AC310613

AH

Connector: C-124 <LHD>

9

21

33

35

24

12

3 4

7

8

5 6

39

28

41

30

18

4243

31

1920

32

40

29

1617

38

27

15

37

36

26

14

13

25

2

1

34

23

11

10

22

AC310614

BB

Connectors: C-01, C-105 <LHD>

C-01

C-105

C-01

C-105

Harness side

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

AC310623

Connector: C-207 <LHD>

AF

3

4

5

1

2

Junction block side

Junction block (Front view)

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55-98

Step 27. Check the wiring harness between C-207 
PTC heater relay 2 connector terminal No.5 and 
C-103 PTC heater connector terminal No.4.

• Check the PTC heater power supply line for open 

circuit.

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.

STEP 28. Check the trouble symptom

 Check that the PTC heater works normally.

Q: Is the check result normal?

YES : 

This diagnosis is complete.

NO : 

Replace the A/C-ECU.

AC310613

AF

Connector: C-103 <LHD>

Harness side

AC310623

Connector: C-207 <LHD>

AF

3

4

5

1

2

Junction block side

Junction block (Front view)

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55-99

INSPECTION PROCEDURE 11: The PTC heater does not work <RHD>

COMMENTS ON TROUBLE SYMPTOM

When the PTC heater does not work under the 
following conditions, the PTC heater switch system 
or the PTC heater circuit system may be defective.

PTC heater operating conditions

• PTC heater switch: ON

• Air outlet: FOOT/DEF, FOOT, FACE/FOOT

• Temperature control dial: MAX HOT

• Coolant temperature: 82 degrees celsius or less

NOTE: When the coolant temperature becomes 
above 82 degrees celsius and PTC heater stops the 
operation, the PTC heater does not operate until 
coolant temperature becomes below 72 degrees 
celsius.

POSSIBLE CAUSES

• Malfunction of the PTC heater switch system

FUSIBLE
LINK

28

IGNITION
SWITCH (IG2)

PTC
HEATER
RELAY 2

PTC
HEATER
RELAY 1

PTC
HEATER

A/C-ECU

Wire colour code
B : Black     LG : Light green     G : Green     L : Blue     W : White     Y : Yellow     SB : Sky blue
BR : Brown     O : Orange     GR : Gray     R : Red     P : Pink     V : Violet

PTC Heater Circuit

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55-100

• Damaged the wiring harness or connectors

• Malfunction of the PTC heater relay 1

• Malfunction of the PTC heater relay 2

• Malfunction of the PTC heater

• Malfunction of the automatic air conditioner 

control panel (A/C-ECU)

DIAGNOSIS

Step 1. MUT-III data list

Check that the following service data display 
contents are normal. (Refer to 

P.55-183

.)

• Item 35: PTC heater switch

Q: Does the blower motor work normally? 

YES : 

Go to Step 4.

NO : 

Go to Step 2.

Step 2. Connector check: C-106 A/C-ECU 
connector

Q: Is the check result normal?

YES : 

Go to Step 3.

NO : 

Repair the connector.

Step 3. Voltage measurement at C-106 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 PTC heater switch to the "ON" position.

(4) Voltage between terminal 26 and body earth.

OK: System voltage

Q: Is the check result normal?

YES : 

 Go to Step 28.

NO : 

Inspection Procedure 25: Refer to PTC 
heater switch system <RHD>

P.55-171

 .

Step 4. Connector check: C-103 PTC heater 
connector

Q: Is the check result normal?

YES : 

Go to Step 5.

NO : 

Repair the connector.

Step 5. Resistance measurement at the C-103 
PTC heater connector.

(1) Disconnect the connector, and measure at the 

AC310631AB

Connectors: C-106 <RHD>

Harness side

AC310631AB

Connectors: C-106 <RHD>

Harness side

AC310507

Connector C-106 
(Harness side)

AT

AC310631AF

Connector: C-103 <RHD>

Harness side

AC310631AF

Connector: C-103 <RHD>

Harness side