Subaru Legacy III (2000-2003 year). Manual - part 439

CO(H4DOSTC)-10

COOLING

RADIATOR MAIN FAN SYSTEM

NOTE:
Inspection by distributor service is required, because probable cause is deterioration of multiple parts.

13

CHECK HARNESS BETWEEN MAIN FAN 
RELAY AND ECM.
1) Turn ignition switch to OFF.
2) Disconnect connector from ECM.
3) Measure resistance of harness between 

main fan relay connector and ECM connec-
tor.

Connector & terminal

(F66) No. 7 — (B134) No. 14:

Is the measured value less than the speci-
fied valve?

1 

Ω

Go to step 14.

Repair open circuit 
in harness 
between main fan 
relay and ECM.

14

CHECK POOR CONTACT.
Check poor contact in connector between main 
fan and ECM.
Is there poor contact in connector between 
main fan motor and ECM?

There is poor contact.

Repair poor con-
tact connector.

Contact with dis-
tributor service.

Step

Value

Yes

No

CO(H4DOSTC)-11

COOLING

RADIATOR SUB FAN SYSTEM

3. Radiator Sub Fan System

A: SCHEMATIC

CO-00146

2

1

4

3

21

22

24

20

8

7

5

9

20A

20A

SUB FAN

RELAY

AIR CONDITIONING RELAY HOLDER

SUB FAN

MOTOR

MAIN FAN

MOTOR

MAIN FAN

RELAY

F28

F16

F66

F27

1

2

F17

B100

F2

B72

1

2

8
9

NO. 3

NO. 18

NO. 17

SBF-4

SBF-1

IGNITION 
SWITCH

B72

3 4

1 2

B137

BATTERY

17

28

B137

ECM

F16

F17

2 1

F27

1

2

3

4

5 6 7

8
9

11

10

13

12

14

21

20

23

22

24

31

30

33

32

34

16

15

17

18
19

26

25

27

28
29

35

36

F66

F28

F2

1

2 3 4

5 6 7

9 10 11 12 13 14 15 16

8

1

2

7

8

9

5

6

3

4

10

11

12

19

20

21

29

30

31

13

14

15

16

17

27

28

18

22

23

24

25

26

CO(H4DOSTC)-12

COOLING

RADIATOR SUB FAN SYSTEM

B: INSPECTION

NOTE:
Radiator sub fan system is for model with A/C.
DETECTING CONDITION:
Condition (1):
• Engine coolant temperature is below 95

°

C (203

°

F).

• A/C switch is turned ON.
• Vehicle speed is below 19 km/h (12 MPH).
Condition (2):
• Engine coolant temperature is above 100

°

C (212

°

F).

• A/C switch is turned OFF.
• Vehicle speed is below 19 km/h (12 MPH).
TROUBLE SYMPTOM:
• Radiator sub fan does not rotate under conditions (1) and (2) above.

Step

Value

Yes

No

1

CHECK POWER SUPPLY TO SUB FAN MO-
TOR.

CAUTION:

Be careful not to overheat engine during re-
pair.

1) Turn ignition switch to OFF.
2) Disconnect connector from sub fan motor 

and main fan motor.

3) Start the engine, and warm it up until 

engine coolant temperature increases over 
100

°

C (212

°

F).

4) Stop the engine and turn ignition switch to 

ON.

5) Measure voltage between sub fan motor 

connector and chassis ground.

Connector & terminal

(F16) No. 2 (+) — Chassis ground (

−−−−

):

Does the measured value exceed the spec-
ified value?

10 V

Go to step 2.

Go to step 5.

2

CHECK GROUND CIRCUIT OF SUB FAN 
MOTOR.
1) Turn ignition switch to OFF.
2) Measure resistance between sub fan motor 

connector and chassis ground.

Connector & terminal

(F16) No. 1 — Chassis ground:

Is the measured value less than the speci-
fied valve?

5 

Ω

Go to step 3.

Repair open circuit 
in harness 
between sub fan 
motor connector 
and chassis 
ground.

3

CHECK POOR CONTACT.
Check poor contact in sub fan motor connec-
tor.
Is there poor contact in sub fan motor connec-
tor?

Repair poor con-
tact in sub fan 
motor connector.

Go to step 4.

4

CHECK SUB FAN MOTOR.
Connect battery positive (+) terminal to termi-
nal No. 2, and negative (

−

) terminal to terminal 

No. 1 of sub fan motor connector.
Does the sub fan rotate?

Sub fan rotates.

Repair poor con-
tact in sub fan 
motor connector.

Replace sub fan 
motor with a new 
one.

CO(H4DOSTC)-13

COOLING

RADIATOR SUB FAN SYSTEM

5

CHECK POWER SUPPLY TO SUB FAN RE-
LAY.
1) Turn ignition switch to OFF.
2) Remove sub fan relay from A/C relay 

holder.

3) Measure voltage between sub fan relay ter-

minal and chassis ground.

Connector & terminal

(F28) No. 21 (+) — Chassis ground (

−−−−

):

Does the measured value exceed the spec-
ified value?

10 V

Go to step 6.

Go to step 7.

6

CHECK POWER SUPPLY TO SUB FAN RE-
LAY.
1) Turn ignition switch to ON.
2) Measure voltage between sub fan relay ter-

minal and chassis ground.

Connector & terminal

(F28) No. 24 (+) — Chassis ground (

−−−−

):

Does the measured value exceed the spec-
ified value?

10 V

Go to step 10.

Go to step 9.

7

CHECK 20 A FUSE.
1) Remove 20 A fuse from A/C relay holder.
2) Check condition of fuse.

Is the fuse blown-out?

Fuse is blown-out.

Replace fuse.

Go to step 8.

8

CHECK POWER SUPPLY TO A/C RELAY 
HOLDER 20 A FUSE TERMINAL.
Measure voltage of harness between A/C relay 
holder 20 A fuse terminal and chassis ground.

Connector & terminal

(F27) No. 3 (+) — Chassis ground (

−−−−

):

Does the measured value exceed the specified 
value?

10 V

Repair open circuit 
in harness 
between 20 A fuse 
and sub fan relay 
terminal.

Repair open circuit 
in harness 
between main fuse 
box connector and 
20 A fuse terminal.

9

CHECK FUSE.
1) Turn ignition switch to OFF.
2) Remove fuse No. 17 from joint box.
3) Check condition of fuse.

Is the fuse blown-out?

Fuse is blown-out.

Replace fuse.

Repair open circuit 
in harness 
between sub fan 
relay and ignition 
switch.

10

CHECK SUB FAN RELAY.
1) Turn ignition switch to OFF.
2) Measure resistance of sub fan relay.

Terminal

 No. 20 — No. 21:

Does the measured value exceed the spec-
ified value?

1 M

Ω

Go to step 11.

Replace sub fan 
relay.

11

CHECK SUB FAN RELAY.
1) Connect battery to terminals No. 22 and 

No. 24 of sub fan relay.

2) Measure resistance of sub fan relay.

Terminal

 No. 20 — No. 21:

Is the measured value less than the speci-
fied valve?

1 

Ω

Go to step 12.

Replace sub fan 
relay.

Step

Value

Yes

No