Subaru Legacy IV (2008 year). Service manual - part 996

 

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Subaru Legacy IV (2008 year). Service manual - part 996

 

 

AC(diag)-36

Diagnostic Procedure for Sensors

HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK POWER SUPPLY VOLTAGE FOR 
SUNLOAD SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from sunload 
sensor.
3) Turn the ignition switch to ON.
4) Measure the power supply voltage for sun-
load sensor.

Connector & terminal

(i51) No. 1 (+) — No. 2 (–):

Is the voltage approx. 5 V?

Go to step 4.

Go to step 2.

2

CHECK HARNESS CONNECTOR BETWEEN 
AUTO A/C CONTROL MODULE AND SUN-
LOAD SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from the auto A/C 
control module.
3) Measure the resistance of the harness 
between the auto A/C control module and sun-
load sensor.

Connector & terminal

(i51) No. 2 — (B282) No. 6:

Is the resistance less than 1 

:? Go to step 3.

Repair the harness 
between auto A/C 
control module and 
sunload sensor.

3

CHECK HARNESS CONNECTOR BETWEEN 
AUTO A/C CONTROL MODULE AND SUN-
LOAD SENSOR.
Measure the resistance of the harness between 
the auto A/C control module and sunload sen-
sor.

Connector & terminal

(i51) No. 1 — (B282) No. 8:

Is the resistance less than 1 

:? Go to step 4.

Repair the harness 
between auto A/C 
control module and 
sunload sensor.

4

CHECK INPUT VOLTAGE FOR AUTO A/C 
CONTROL MODULE.
1) Connect the connectors of sunload sensor 
and auto A/C control module.
2) Turn the ignition switch to ON.
3) Measure the voltage between connector 
terminals of auto A/C control module.

Connector & terminal

(B282) No. 8 (+) — (B282) No. 6 (–):

Is the voltage approx. 2.5 V?

Go to step 5.

Replace the sun-
load sensor.

5

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

Is there poor contact in connec-
tor?

Repair the connec-
tor.

Replace the auto 
A/C control mod-
ule.

AC(diag)-37

Diagnostic Procedure for Sensors

HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)

E: A/C LOCK SENSOR

H6 model
WIRING DIAGRAM:

B282

1 2 3 4

5 6 7 8 9

10 11 12 13 14 15 16 17 18 19 20

F37

A:

B135

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

29 30 31

32 33

34 35

B:

F115

1 2

B282

B143

1 2 3 4

5 6 7 8 9

10 11 12 13 14 15 16 17 18 19 20

B:

B122

*

*

*

B135

B14

C24

B136

B:

C:

15

A20

A18

A16

F37

A:

B143

B:

B10

B12

B14

MAIN FUSE

BOX

(M/B)

2

1

F115

 :

*

*

B83

1 2 3 4
5 6 7 8

B122

B83

C: B136

16

10 11 12 13 14 15

25

24

30

9

8

7

17 18 19 20
28

21 22 23

29

32

31

1

2

3

4

5

6

27

26

33 34 35

AC-01653

1 2 3 4 5 6 7 8 9 10

21 22 23 24 25 26 27 28 29 30

11 12 13 14 15 16 17 18 19 20
31 32 33 34 35 36 37 38 39 40

A/C

LOCK

SENSOR

JOINT

CONNECTOR

JOINT
CONNECTOR

AUTO A/C CONTROL MODULE

TERMINAL No. 
OPTIONAL
ARRANGEMENT

ECM

AC(diag)-38

Diagnostic Procedure for Sensors

HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK A/C LOCK SENSOR SIGNAL.
1) Turn the ignition switch to OFF.
2) Connect the Subaru Select Monitor to data 
link connector.
3) Start the engine and turn the A/C switch to 
ON.
4) Read the data of A/C lock signal using Sub-
aru Select Monitor.

NOTE:
• Subaru Select Monitor
For detailed operation procedure, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H6DO)(diag)-35, READ CURRENT
DATA FOR ENGINE (NORMAL MODE), OP-
ERATION, Subaru Select Monitor.>

Is the A/C lock signal switch 
ON?

Go to step 4.

Go to step 2.

2

CHECK A/C LOCK SENSOR SIGNAL.
1) Start the engine and turn the A/C switch to 
ON.
2) Measure the voltage between auto A/C con-
trol module connector and chassis ground.

Connector & terminal

(B282) No. 15 (+) — Chassis ground (–):

Is the voltage 7 — 14 V?

Replace the auto 
A/C control mod-
ule.

Go to step 3.

3

CHECK ECM OUTPUT.
Measure the voltage between ECM and chassis 
ground.

Connector & terminal

(B136) No. 24 (+) — Chassis ground (–):

Is the voltage 7 — 14 V?

Repair the harness 
between ECM and 
auto A/C control 
module.

Replace the ECM.

4

CHECK A/C LOCK SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between ECM con-
nector and chassis ground.

Connector & terminal

(B135) No. 14 — Chassis ground:

Is the resistance between 240 
— 290 

:?

Replace the ECM. Go to step 5.

5

CHECK A/C LOCK SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the main fuse box connector.
3) Measure the resistance between main fuse 
box terminal.

Connector & terminal

(F37) No. 16 — No. 18:

Is the resistance between 240 
— 290 

:?

Go to step 7.

Go to step 6.

6

CHECK A/C LOCK SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the A/C lock sensor connector.
3) Measure the resistance between A/C lock 
sensor terminals.

Connector & terminal

(F115) No. 1 — No. 2:

Is the resistance between 240 
— 290 

:?

Repair or replace 
the harness 
between A/C lock 
sensor and main 
fuse box.

Replace the A/C 
compressor 
assembly. (A/C 
lock switch mal-
function)

7

CHECK MAIN FUSE BOX.
1) Turn the ignition switch to OFF.
2) Disconnect the connector and then mea-
sure the resistance between main fuse box ter-
minal.

Connector & terminal

(F37) No. 16 — (B143) No. 14:
(F37) No. 18 — (B143) No. 12:

Is the resistance less than 10 

:? Repair or replace 

the harness 
between A/C lock 
sensor and main 
fuse box.

Replace the main 
fuse box.

AC(diag)-39

Diagnostics with Phenomenon

HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)

9. Diagnostics with Phenomenon

A: INSPECTION

Symptom

Problem parts

A/C system fails to operate.

• Fuse (M/B No. 8, F/B No. 22, 31)
• Connector (Poor contact)
• Ground
• Auto A/C control module
• Blower fan motor
• Blower fan relay
• A/C relay
• Compressor (Magnet clutch)
• Evaporator sensor

Fuse is blown out.

• Fuse (M/B No. 8, F/B No. 22, 31)
• Connector (Poor contact)

Illumination cannot dim.

• Fuse (M/B No. 8, F/B No. 22, 31)
• Connector (Poor contact)
• Auto A/C control module
• Body integrated unit

Blower fan does not rotate or fan speed cannot be controlled.

• Fuse (F/B No. 22, 27, 28)
• Connector (Poor contact)
• Ground
• Auto A/C control module
• Blower fan motor
• Blower fan relay

Unable to switch suction vents.

• Connector (Poor contact)
• Auto A/C control module
• Intake door actuator

Unable to switch vents.

• Connector (Poor contact)
• Auto A/C control module
• Mode door actuator

The compartment temperature does not rise. (Warm air does 
not come out.)

• Connector (Poor contact)
• Auto A/C control module
• Air mix door actuator
• In-vehicle sensor, ambient sensor, evaporator sensor and 
sunload sensor
• In-vehicle sensor aspirator hose

The compartment temperature does not lower. (Cold air does 
not come out.)

• Connector (Poor contact)
• Auto A/C control module
• Air mix door actuator
• A/C relay
• Compressor (Magnet clutch)
• Radiator fan motor
• Radiator fan relay
• In-vehicle sensor, ambient sensor, evaporator sensor and 
sunload sensor
• In-vehicle sensor aspirator hose

Compartment temperature is higher or lower than setting tem-
perature.

• Auto A/C control module
• Air mix door actuator
• In-vehicle sensor, ambient sensor, evaporator sensor and 
sunload sensor
• In-vehicle sensor aspirator hose

Compartment temperature does not quickly respond to setting 
temperature.

• Air mix door actuator
• In-vehicle sensor, ambient sensor, evaporator sensor and 
sunload sensor
• In-vehicle sensor aspirator hose

Radiator fan does not rotate during A/C operation.

• Radiator fan motor
• Radiator fan relay

 

 

 

 

 

 

 

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