Subaru Legacy IV (2008 year). Manual - part 989

AC(diag)-8

Auto A/C Control Module I/O Signal

HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)

*1: Battery voltage cannot be measured because of digital signal.

B: WIRING DIAGRAM

1. AIR CONDITIONER AUTO A/C MODEL

<Ref. to WI-111, WIRING DIAGRAM, Air Conditioning System.>

20

Intake door actuator drive signal

When intake door actuator is operating

0.7 V or less

40

21

Ignition power supply

Ignition switch: ON

Battery voltage

22

Pressure switch signal

Ignition switch: ON

Normal: ON

Abnormal: OFF

24

Air mix door actuator (driver’s side) 
position signal

Air mix door: Maximum cool position

4 V

Air mix door: Maximum hot position

1 V

25

After-evaporator sensor signal

Changes by the temperature after the evaporator

1 — 4.5 V

26

VER switching signal (FOOT switch)

When switching FOOT

0 V

27

Sensor ground

Always

0 V

28

Control module ground

Always

0 V

32

Heater main relay drive signal

Ignition switch: ON

Battery voltage

33

RAM monitor ON signal

RAM monitor ON

0 V

34

Heater control panel communication

 — 

*1

35

Heater control panel communication

 — 

*1

Terminal No.

Remarks

Measuring condition

Standard

AC(diag)-9

Diagnostic Chart for Self-Diagnosis

HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)

5. Diagnostic Chart for Self-Diagnosis

A: OPERATION

NOTE:
For A/C system self-diagnosis, there is one that checks the control panel, and the other that checks the whole
control system (sensor, actuator, blower motor, etc.). Perform the self-diagnosis for control panel first, and
then perform the self-diagnosis for control system.

(1)

Front defroster switch

(4)

Air flow control switch

(7)

FRESH/RECIRC switch

(2)

Rear window defogger switch

(5)

FAN switch

(8)

OFF switch

(3)

A/C switch

(6)

AUTO switch

 

 

(8)

(7)

(6)

(4)

(5)

(1)

(2)

(3)

AC-01536

AC(diag)-10

Diagnostic Chart for Self-Diagnosis

HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)

1. A/C CONTROL PANEL SELF-DIAGNOSIS

Step

Check

Yes

No

1

PERFORM A/C CONTROL PANEL SELF-DI-
AGNOSIS FUNCTION.
1) Turn the ignition switch to OFF.
2) Turn the ignition switch to ON with the AUTO 
switch and MODE switch pressed at the same 
time.
3) All the screen display illuminate (for approx. 
5 seconds) and the self-diagnosis mode starts.

Does the self-diagnosis func-
tion operate?

Go to step 2.

<Ref. to AC(diag)-
14, A/C OR SELF-
DIAGNOSIS SYS-
TEMS DO NOT 
OPERATE, Diag-
nostics for A/C 
System Malfunc-
tion.>

2

CHECK SCREEN DISPLAY.
Check the illumination condition while the dis-
play is illuminated.

Does all the screen display and 
indicators illuminate?

Go to step 3.

Replace the A/C 
control panel.

3

CHECK SCREEN DISPLAY.
After the illumination ends, check the display.

Are the numbers 11 — 14 dis-
played at the setting tempera-
ture display area?

Go to step 5.

Go to step 4.

4

CHECK SWITCH AND TEMPERATURE CON-
TROL DIAL INPUT.
1) Operate each switch or dial according to the 
switch check table.
2) Check the display or indicator illumination 
condition when operating the switch or dial. 
<Ref. to AC(diag)-11, SWITCH CHECK TABLE, 
OPERATION, Diagnostic Chart for Self-Diagno-
sis.>

Does the input of each switch or 
dial correspond to the switch 
check list?

Go to step 5.

Replace the heater 
control panel.

5

CHECK A/C CONTROL PANEL COMMUNI-
CATION.
1) Turn the ignition switch to OFF.
2) Disconnect the connector of the auto A/C 
control module.
3) Using a suitable lead wire, short the termi-
nal No. 34 and No. 35 of auto A/C control mod-
ule vehicle side connector (B282).
4) Turn the ignition switch to ON with the A/C 
switch and AUTO switch pressed at the same 
time.
5) Check the screen display when operating 
each switch and dial.

Is “CL” displayed on the screen 
when operating each switch 
and dial?

Go to step 6.

Go to step 7.

6

CHECK A/C CONTROL PANEL COMMUNI-
CATION.
1) Turn the ignition switch to OFF.
2) Disconnect the lead wire used to short the 
terminals.
3) Turn the ignition switch to ON with the A/C 
switch and AUTO switch pressed at the same 
time.
4) Check the screen display when operating 
each switch and dial.

Is “OP” displayed on the screen 
when operating each switch 
and dial?

A/C control panel 
and body harness 
are normal.

Go to step 7.

7

CHECK HARNESS.
1) Turn the ignition switch to OFF.
2) Disconnect the A/C control panel connector 
(i88).
3) Measure the resistance between connec-
tors with a tester.

Connector & terminal

(i88) No. 7 — (B282) No. 34:
(i88) No. 3 — (B282) No. 35:

Is the resistance less than 10 

:? Go to step 8.

Repair the open 
circuit of the har-
ness between A/C 
control panel and 
auto A/C control 
module.

AC(diag)-11

Diagnostic Chart for Self-Diagnosis

HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)

2. SWITCH CHECK TABLE

8

CHECK HARNESS.
Measure the resistance between connectors 
with a tester.

Connector & terminal

(i88) No. 7 — No. 3:

Is the resistance less than 10 
:?

Repair the short 
circuit of the har-
ness between A/C 
control panel and 
auto A/C control 
module.

Replace the A/C 
control panel.

Switch

Display screen

Switch

Display screen

A/C switch

(6)

FAN switch (+)

(4)

AUTO switch

(1)

FAN switch (–)

(3)

Air flow control switch

(9)

Driver’s side temperature control dial

(9), (10), (12)

FRESH/RECIRC

(13)

Passenger’s side temperature control dial

(9), (11), (12)

Defroster switch

(7), (12)

OFF switch

(2), (5)

Rear defogger switch

(8)

 

 

Step

Check

Yes

No

(11)

(4)

(5)

(6)

(3)

(2)

(1)

(10)

(9)

(12)

(13)

(7)

(8)

AC-01684