Subaru Legacy (2005 year). Manual - part 878

AC(diag)-29

HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)

Diagnostic Procedure for Actuators

Step

Check

Yes

No

1

CHECK POWER SUPPLY FOR AIR MIX 
DOOR ACTUATOR POSITION SWITCH.
1) Turn the ignition switch to OFF.
2) Disconnect the air mix door actuator con-
nector.
3) Turn the ignition switch and AUTO switch to 
ON.
4) Measure the voltage between auto A/C 
control module connector terminals.

Connector & terminal

(B282) No. 8 (+) — (B282) No. 15 (

−

):

Is the voltage approx. 5 V?

Go to step 2.

Replace the auto 
A/C control mod-
ule.

2

CHECK POWER SUPPLY FOR AIR MIX 
DOOR ACTUATOR.
Measure the voltage between auto A/C control 
module connector and chassis ground after 
turning the temperature control dial to maxi-
mum COOL position.

Connector & terminal

(B283) No. 8 (+) — Chassis ground (

−

):

Is the voltage 7 V (at normal 
temperature)?

Go to step 3.

Replace the auto 
A/C control mod-
ule.

3

CHECK POWER SUPPLY FOR AIR MIX 
DOOR ACTUATOR.
Measure the voltage between auto A/C control 
module connector and chassis ground after 
turning the temperature control dial to maxi-
mum HOT position.

Connector & terminal

(B283) No. 18 (+) — Chassis ground (

−

):

Is the voltage 7 V (at normal 
temperature)?

Go to step 4.

Replace the auto 
A/C control mod-
ule.

4

CHECK HARNESS BETWEEN AUTO A/C 
CONTROL MODULE AND AIR MIX DOOR 
ACTUATOR.
1) Turn the A/C and ignition switch to OFF.
2) Disconnect the auto A/C control module 
connector.
3) Measure the resistance between auto A/C 
control module and air mix door actuator con-
nector.

Connector & terminal

(B235) No. 1 — (B282) No. 8:
(B235) No. 3 — (B282) No. 15:
(B235) No. 5 — (B282) No. 4:
(B235) No. 6 — (B283) No. 8:
(B235) No. 7 — (B283) No. 18:

Is the resistance less than 1 
Ω?

Go to step 5.

Repair the har-
ness between auto 
A/C control mod-
ule and air mix 
door actuator.

5

CHECK AIR MIX DOOR ACTUATOR POSI-
TION SWITCH SIGNAL.
1) Connect the connector of auto A/C control 
module and air mix door actuator.
2) Turn the ignition switch and AUTO switch to 
ON.
3) Check the voltage between auto A/C con-
trol module connector terminals while chang-
ing the setting temperature between maximum 
COOL and maximum HOT.

Connector & terminal

(B282) No. 4 (+) — (B282) No. 15 (

−

):

Does the voltage change 
between 1 (maximum HOT) — 
4 (maximum COOL) V?

Go to step 6.

Replace the air 
mix door actuator.

6

CHECK POOR CONTACT.
Check poor contact in auto A/C control module 
and connector.

Is there poor contact in con-
nector?

Repair the con-
nector.

Replace the auto 
A/C control mod-
ule.

AC(diag)-30

HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)

Diagnostic Procedure for Sensors

8. Diagnostic Procedure for Sensors

A: AMBIENT SENSOR

TROUBLE SYMPTOM:
Fan speed is not switched when the fan speed control dial is in AUTO position.
WIRING DIAGRAM:

AC-00829

B283

F78

AUTO A/C

CONTROL MODULE

AMBIENT SENSOR

B1

B11

3 4

1 2

8 9 10

11 12 13 14 15 16 17 18 19 20

5 6 7

B283

2

1

F78

1 2

10

11

14

13

B26

B25

C3

C10

F108

B361

B280

B281

B: 

C: 

5

4

6 7

8

2

1

9

3

10

22

23

11 12 13 14 15

24 25

26 27

16 17 18

28 29

19 20

21

30

B280

B281

B:

5 6 7

8

2

1

9

4

3

10

24

22 23

25

11 12 13 14 15

26

27 28

16 17 18 19

20 21

C:

1 2 3

4 5 6

7 8 9 10 11 12 13 14

B361

1 2 3

8

9 10

4

11 12 13 14 15 16

5 6 7

17 18

F108

THROUGH
JOINT CONNECTOR

BODY INTEGRATED MODULE

AC(diag)-31

HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)

Diagnostic Procedure for Sensors

Step

Check

Yes

No

1

CHECK AMBIENT SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ambient 
sensor.
3) Measure the resistance between connector 
terminals of ambient sensor.

Terminals

No. 1 — No. 2:

Is the resistance approx. 2.2 
k

Ω at 25°C (77°F)?

Go to step 2.

Replace the ambi-
ent sensor.

2

CHECK INPUT SIGNAL FOR AMBIENT SEN-
SOR.
1) Turn the ignition to ON.
2) Measure the voltage between connector 
(F78) terminals.

Connector & terminal

(F78) No. 1 (+) — No. 2 (

−

):

Is the voltage approx. 5 V?

Go to step 6.

Go to step 3.

3

CHECK OUTPUT SIGNAL OF BODY INTE-
GRATED MODULE.
1) Turn the ignition switch to OFF.
2) Draw out the body integrated module.
3) Disconnect the connector from ambient 
sensor.
4) Turn the ignition switch to ON.
5) Measure the voltage between connector 
terminals of body integrated module.

Connector & terminal

(B281) No. 3 (+) — No. 10 (

−

):

Is the voltage approx. 5 V?

Go to step 4.

Go to step 6.

4

CHECK HARNESS CONNECTOR BETWEEN 
BODY INTEGRATED MODULE AND AMBI-
ENT SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from body inte-
grated module.
3) Measure the resistance in harness 
between body integrated module and ambient 
sensor.

Connector & terminal

(F78) No. 1 — (B281) No. 10:

Is the resistance less than 1 
Ω?

Go to step 5.

Repair the open 
circuit in harness 
between body inte-
grated module and 
ambient sensor.

5

CHECK HARNESS CONNECTOR BETWEEN 
BODY INTEGRATED MODULE AND AMBI-
ENT SENSOR.
Measure the resistance in harness between 
body integrated module and ambient sensor.

Connector & terminal

(F78) No. 2 — (B281) No. 3:

Is the resistance less than 1 
Ω?

Go to step 6.

Repair the open 
circuit in harness 
between body inte-
grated module and 
ambient sensor.

6

CHECK COMMUNICATION ERROR DIS-
PLAY.
1) Connect the connectors of body integrated 
module and ambient sensor.
2) Check “Er lu” is indicated on the Odo/Trip 
meter in combination meter after turning the 
ignition switch to ON.

Is the error display “Er lu” indi-
cated?

Replace the body 
integrated mod-
ule. <Ref. to SL-
44, REMOVAL, 
Body Integrated 
Module.>

Go to step 7.

AC(diag)-32

HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)

Diagnostic Procedure for Sensors

7

CHECK COMMUNICATION ERROR DIS-
PLAY.
Check “Er LC” is indicated on the Odo/Trip 
meter in combination meter after turning the 
ignition switch to ON.

Is the error display “Er LC” indi-
cated?

Go to step 8.

Read the Diagnos-
tic Trouble Code 
(DTC) for body 
integrated mod-
ule, and perform 
the diagnosis 
according to DTC. 
<Ref. to 
LAN(diag)-14, 
READ DIAGNOS-
TIC TROUBLE 
CODE (DTC), 
OPERATION, 
Subaru Select 
Monitor.>

8

CHECK HARNESS CONNECTOR BETWEEN 
BODY INTEGRATED MODULE AND AUTO 
A/C CONTROL MODULE.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from body inte-
grated module.
3) Disconnect auto A/C control module con-
nector.
4) Measure the resistance in harness 
between body integrated module and auto A/C 
control module.

Connector & terminal

(B280) No. 25 — (B283) No. 11:

Is the resistance less than 1

Ω? Go to step 9.

Repair the open 
circuit in harness 
between body inte-
grated module and 
auto A/C control 
module. <Ref. to 
LAN(diag)-5, LAN 
SYSTEM, CAU-
TION, General 
Description.>

9

CHECK HARNESS CONNECTOR BETWEEN 
BODY INTEGRATED MODULE AND AUTO 
A/C CONTROL MODULE.
Measure the resistance in harness between 
body integrated module and auto A/C control 
module.

Connector & terminal

(B280) No. 25 — (B283) No. 1:

Is the resistance less than 1

Ω? Go to step 10.

Repair the open 
circuit in harness 
between body inte-
grated module and 
auto A/C control 
module. <Ref. to 
LAN(diag)-5, LAN 
SYSTEM, CAU-
TION, General 
Description.>

10

CHECK POOR CONTACT.
Check poor contact in auto A/C control module 
connector.

Is there poor contact in con-
nector?

Repair the con-
nector.

Replace the A/C 
control module.

Step

Check

Yes

No