Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Manual — part 607

AC(diag)-33

Diagnostic Procedure for Sensors

HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)

C: EVAPORATOR SENSOR

WIRING DIAGRAM:

Air conditioning system, auto A/C model <Ref. to WI-77, AUTO A/C MODEL, WIRING DIAGRAM, Air Con-

ditioning System.>

Step

Check

Yes

No

1

CHECK EVAPORATOR SENSOR.
Perform the inspection of evaporator sensor
unit. <Ref. to AC-40, EVAPORATOR SENSOR,
INSPECTION, Evaporator.>

Is the evaporator sensor nor-
mal?

Go to step

2.

Replace the evap-
orator sensor.
<Ref. to AC-37,
REMOVAL, Evapo-
rator.>

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. 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

(i88) No. 18 (+) — (i88) No. 14 (–):

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 the auto A/C
control module.
3) Measure the resistance of harness between
auto A/C control module and evaporator sensor.

Connector & terminal

(B88) No. 2 — (i88) No. 18:

Is the resistance less than 1 Ω? Go to step

5.

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

i1

5 6 7 8

2

1

9

4

3

10

24

22

23

25

27

26

28

11 12 13

14 15 16

17 18 19 20 21

9

10

1 2

i1

B36

i88

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

B88

2

1

B88

14

1

8

i88

AC-02431

AUTO A/C

CONTROL MODULE

EVAPORATOR SENSOR

AC(diag)-34

Diagnostic Procedure for Sensors

HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)

5

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

Connector & terminal

(B88) No. 1 — (i88) No. 14:

Is the resistance less than 1 Ω? Go to step

6.

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

6

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

Is there poor contact of connec-
tor?

Repair the connec-
tor.

Replace the auto
A/C control mod-
ule. <Ref. to AC-
31, REMOVAL,
Control Unit (Auto
A/C Model).>

Step

Check

Yes

No

AC(diag)-35

Diagnostic Procedure for Sensors

HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)

D: SUNLOAD SENSOR

TROUBLE SYMPTOM:

• Sensor identifies that sunlight is at maximum. Then, A/C system is controlled to COOL side.

• Sensor identifies that sunlight is at minimum. Then, A/C system is controlled to HOT side.
NOTE:

When the sunload sensor check is performed indoors or in the shade, it could be diagnosed as having an

open circuit. Always check the sunload sensor with the sun shining on it.

WIRING DIAGRAM:

Air conditioning system, auto A/C model <Ref. to WI-77, AUTO A/C MODEL, WIRING DIAGRAM, Air Con-

ditioning System.>

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. 2 (+) — No. 1 (–):

Is the voltage approx. 5 V?

Go to step

4.

Go to step

2.

AC-01702

i88

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

i88

i51

1

2

16

14

i51

1 2

SUNLOAD

SENSOR

AUTO A/C

CONTROL

MODULE

AC(diag)-36

Diagnostic Procedure for Sensors

HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)

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 — (i88) No. 16:

Is the resistance less than 1 Ω? 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 — (i88) No. 14:

Is the resistance less than 1 Ω? 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

(i88) No. 16 (+) — (i88) No. 14 (–):

Is the voltage between approx.
1.0 — 4.0 V?

Go to step

5.

Replace the sun-
load sensor. <Ref.
to AC-46,
REMOVAL, Sun-
load Sensor (Auto
A/C Model).>

5

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

Is there poor contact of connec-
tor?

Repair the connec-
tor.

Replace the auto
A/C control mod-
ule. <Ref. to AC-
31, REMOVAL,
Control Unit (Auto
A/C Model).>

Step

Check

Yes

No