Subaru Legacy (2005 year). Manual - part 879

AC(diag)-33

HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)

Diagnostic Procedure for Sensors

B: IN-VEHICLE SENSOR

TROUBLE SYMPTOM:
Blower fan speed, air flow outlet and air flow inlet do not change after turning the AUTO switch to ON.
WIRING DIAGRAM:

AC-00830

A: B282

1 2 3 4 5 6 7 8
9 10 11 12 13 14 15 16

i55

A: B282

A15

A5

2

1

i3

B38

i55

1 2

IN-VEHICLE

SENSOR

AUTO A/C 

CONTROL MODULE

12

11

1 2 3 4

5 6 7 8 9

10 11 12 13 14 15 16 17 18 19 20

B38

AC(diag)-34

HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)

Diagnostic Procedure for Sensors

Step

Check

Yes

No

1

CHECK IN-VEHICLE SENSOR.
1) Turn the ignition switch to OFF.
2) Remove the driver’s side lower cover.
3) Disconnect the connector from in-vehicle 
sensor.
4) Measure the resistance between connector 
terminals of in-vehicle sensor.

Terminals

No. 1 — No. 2:

Is the resistance approx. 2.7 
k

Ω at 20°C (68°F)?

Go to step 2.

Replace the in-
vehicle sensor.

2

CHECK INPUT SIGNAL FOR IN-VEHICLE 
SENSOR.
1) Turn the ignition switch to ON.
2) Measure the voltage between connector 
(i55) terminals.

Connector & terminal

(i55) No. 2 (+) — No. 1 (

−

):

Is the voltage approx. 5 V?

Go to step 6.

Go to step 3.

3

CHECK AUTO A/C CONTROL MODULE 
OUTPUT SIGNAL.
1) Turn the ignition switch to OFF.
2) Remove the auto A/C control module.
3) Turn the ignition switch to ON.
4) Measure the voltage between connector 
terminals of auto A/C control module.

Connector & terminal

(B282) No. 5 (+) — (B282) No. 15 (

−

):

Is the voltage approx. 5 V?

Go to step 4.

Go to step 6.

4

CHECK HARNESS BETWEEN AUTO A/C 
CONTROL MODULE AND IN-VEHICLE SEN-
SOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from auto A/C 
control module.
3) Measure the resistance in harness 
between auto A/C control module and in-vehi-
cle sensor.

Connector & terminal

(i55) No. 2 — (B282) No. 5:

Is the resistance less than 1 
Ω?

Go to step 5.

Repair the har-
ness between auto 
A/C control mod-
ule and in-vehicle 
sensor.

5

CHECK HARNESS BETWEEN AUTO A/C 
CONTROL MODULE AND IN-VEHICLE SEN-
SOR.
Measure the resistance in harness between 
auto A/C control module and in-vehicle sensor.

Connector & terminal

(i55) No. 1 — (B282) No. 15:

Is the resistance less than 1 
Ω?

Go to step 6.

Repair the har-
ness between auto 
A/C control mod-
ule and in-vehicle 
sensor.

6

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 auto 
A/C control mod-
ule.

AC(diag)-35

HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)

Diagnostic Procedure for Sensors

C: EVAPORATOR SENSOR

WIRING DIAGRAM:

AC-00831

A13

A15

B88

1

2

EVAPORATOR

SENSOR

B88

B282

A:

AUTO A/C

CONTROL MODULE

1
2

1
2

3 4

1 2

8

9 10 11 12 13 14 15 16

5 6 7

B282

A:

AC(diag)-36

HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)

Diagnostic Procedure for Sensors

Step

Check

Yes

No

1

CHECK EVAPORATOR SENSOR
1) Turn the ignition switch to OFF.
2) Remove the glove box.
3) Disconnect the connector from evaporator 
sensor.
4) Measure the resistance between connector 
terminals of evaporator sensor.

Terminals

No. 1 — No. 2:

Is the resistance approx. 3.3 
k

Ω at 20°C (68°F)?

Go to step 2.

Replace the evap-
orator sensor.

2

CHECK INPUT SIGNAL FOR EVAPORATOR 
SENSOR.
1) Turn the ignition switch to ON.
2) Measure the voltage between connector 
(B88) terminals.

Connector & terminal

(B88) No. 1 (+) — No. 2 (

−

):

Is the voltage approx. 5 V?

Go to step 6.

Go to step 3.

3

CHECK AUTO A/C CONTROL MODULE 
OUTPUT SIGNAL.
1) Turn the ignition switch to OFF.
2) Remove the auto A/C control module.
3) Turn the ignition switch to ON.
4) Measure the voltage between connector 
terminals of auto A/C control module.

Connector & terminal

(B282) No. 13 (+) —No. 15 (

−

):

Is the voltage approx. 5 V?

Go to step 4.

Go to step 6.

4

CHECK HARNESS CONNECTOR BETWEEN 
AUTO A/C CONTROL MODULE AND EVAP-
ORATOR SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from auto A/C 
control module.
3) Measure the resistance in harness 
between auto A/C control module and evapo-
rator sensor.

Connector & terminal

(B88) No. 2 — (B282) No. 15:

Is the resistance less than 1 
Ω?

Go to step 5.

Repair the open 
circuit in harness 
between auto A/C 
control module 
and evaporator 
sensor.

5

CHECK HARNESS CONNECTOR BETWEEN 
AUTO A/C CONTROL MODULE AND EVAP-
ORATOR SENSOR.
Measure the resistance in harness between 
auto A/C control module and evaporator sen-
sor.

Connector & terminal

(B88) No. 1 — (B282) No. 13:

Is the resistance less than 1 
Ω?

Go to step 6.

Repair the open 
circuit in harness 
between auto A/C 
control module 
and evaporator 
sensor.

6

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 auto 
A/C control mod-
ule.