Subaru Legacy III (2000-2003 year). Manual - part 280

CO(H6DO)-18

COOLING

RADIATOR SUB FAN SYSTEM

18

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 sub fan motor connector.
3) Start the engine, and perform checking pro-

cedure during coolant temperature is 98 — 
101

°

C (208 — 214

°

F).

4) Measure voltage between sub fan motor 

connector and chassis ground.

Connector & terminal

(F16) No. 1 (+) — Chassis ground (

−−−−

):

Does the measured value exceed the spec-
ified value?

10 V

Go to step 19.

Go to step 21.

19

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

There is poor contact.

Repair poor con-
tact in sub fan 
motor connector.

Go to step 20.

20

CHECK SUB FAN MOTOR.
Connect battery positive (+) terminal to termi-
nal No. 1, and negative (

−

) terminal to terminal 

No. 4 of sub fan motor connector.
Does the sub fan rotate?

Rotates.

Repair poor con-
tact in sub fan 
motor connector.

Replace sub fan 
motor with a new 
one.

21

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

holder.

3) Measure voltage between sub fan relay 1 

terminal and chassis ground.

Connector & terminal

(F28) No. 28 (+) — Chassis ground (

−−−−

):

Does the measured value exceed the spec-
ified value?

10 V

Go to step 22.

Go to step 23.

22

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

terminal and chassis ground.

Connector & terminal

(F28) No. 25 (+) — Chassis ground (

−−−−

):

Does the measured value exceed the spec-
ified value?

10 V

Go to step 26.

Go to step 25.

23

CHECK 30 A FUSE.
1) Remove 30 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 24.

24

CHECK POWER SUPPLY TO A/C RELAY 
HOLDER 30 A FUSE TERMINAL.
Measure voltage of harness between A/C relay 
holder 30 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 30 A fuse 
and sub fan relay 
1 terminal.

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

Step

Value

Yes

No

CO(H6DO)-19

COOLING

RADIATOR SUB FAN SYSTEM

25

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 1 and ignition 
switch.

26

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

Terminal

No. 28 — No. 29:

Does the measured value exceed the spec-
ified value?

1 M

Ω

Go to step 27.

Replace sub fan 
relay 1.

27

CHECK SUB FAN RELAY.
1) Connect battery to terminals No. 25 and 

No. 27 of sub fan relay 1.

2) Measure resistance of sub fan relay 1.

Terminal

No. 28 — No. 29:

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

1 

Ω

Go to step 28.

Replace sub fan 
relay 1.

28

CHECK HARNESS BETWEEN SUB FAN RE-
LAY 1 AND SUB FAN MOTOR CONNECTOR.
Measure resistance of harness between sub 
fan motor connector and sub fan relay 1 termi-
nal.

Connector & terminal

(F16) No. 1 — (F28) No. 29:

Is the measured value less than the specified 
value?

1 

Ω

Go to step 29.

Replace open cir-
cuit in harness 
between sub fan 
motor connector 
and sub fan relay 
1 terminal.

29

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

sub fan relay 1 connector and ECM con-
nector.

Connector & terminal

(F28) No. 27 — (B137) No. 28:

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

1 

Ω

Go to step 30.

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

30

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

There is poor contact.

Repair poor con-
tact connector.

Contact SUBARU 
distributor service.

Step

Value

Yes

No

CO(H6DO)-20

COOLING

RADIATOR SUB FAN SYSTEM

31

CHECK HARNESS BETWEEN SUB FAN MO-
TOR CONNECTOR AND CHASSIS 
GROUND.
1) Turn ignition switch to OFF.
2) Disconnect sub fan motor connector.
3) Turn A/C switch ON and set the tempera-

ture at the lowest position.

4) Perform checking procedure during coolant 

temperature is 98 — 101

°

C (208 — 214

°

F).

5) Measure resistance of harness between 

sub fan motor connector and chassis 
ground.

Connector & terminal

(F16) No. 3 — Chassis ground:

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

5 

Ω

Go to step 32.

Go to step 33.

32

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

There is poor contact.

Repair poor con-
tact in sub fan 
motor connector.

Replace sub fan 
motor with a new 
one.

33

CHECK HARNESS BETWEEN SUB FAN 
AND FAN RELAY.
1) Disconnect fan relay connector.
2) Measure resistance between sub fan motor 

connector and fan relay connector.

Connector & terminal

(F16) No. 3 — (B253) No. 5:

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

1 

Ω

Go to step 34.

Repair open circuit 
between sub fan 
motor connector 
and fan relay con-
nector.

34

CHECK POWER SUPPLY TO FAN RELAY.
1) Turn ignition switch to ON.
2) Measure voltage between fan relay termi-

nal and chassis ground.

Connector & terminal

(B253) No. 1 (+) — Chassis ground (

−−−−

):

Does the measured value exceed the spec-
ified value?

10 V

Go to step 36.

Go to step 35.

35

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 fan relay 
and ignition 
switch.

36

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

Terminal

No. 4 — No. 5:

Does the measured value exceed the spec-
ified value?

1 M

Ω

Go to step 37.

Replace fan relay.

37

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

3 of fan relay.

2) Measure resistance of fan relay.

Terminal

No. 4 — No. 5:

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

1 

Ω

Go to step 38.

Replace fan relay.

Step

Value

Yes

No

CO(H6DO)-21

COOLING

RADIATOR SUB FAN SYSTEM

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

38

CHECK HARNESS BETWEEN FAN RELAY 
TERMINAL AND CHASSIS GROUND.
Measure resistance of harness between fan 
relay connector and chassis ground.

Connector & terminal

(B253) No. 4 — Chassis ground:

Is the measured value less than the specified 
value?

1 

Ω

Go to step 39.

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

39

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

fan relay connector and ECM connector.

Connector & terminal

(B253) No. 3 — (B137) No. 24:

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

1 

Ω

Go to step 40.

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

40

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

There is poor contact.

Repair poor con-
tact connector.

Contact SUBARU 
distributor service.

Step

Value

Yes

No