Subaru IMPREZA GD 2007 Series Manual page 3891

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HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)
Step
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:
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 (–):
3 CHECK AUTO A/C CONTROL MODULE
OUTPUT SIGNAL.
1) Turn the ignition switch to OFF.
2) Pull out the auto A/C control module.
3) Disconnect the connector from ambient
sensor.
4) Turn the ignition switch to ON.
5) Measure the voltage between connector
terminals of auto A/C control module.
Connector & terminal
(B283) No. 9 (+) — No. 17 (–):
4 CHECK HARNESS CONNECTOR BETWEEN
AUTO A/C CONTROL MODULE AND AMBI-
ENT 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 auto A/C control module and ambient
sensor.
Connector & terminal
(F78) No. 1 — (B283) No. 9:
5 CHECK HARNESS CONNECTOR BETWEEN
AUTO A/C CONTROL MODULE AND AMBI-
ENT SENSOR.
Measure the resistance of the harness between
auto A/C control module and ambient sensor.
Connector & terminal
(F78) No. 2 — (B283) No. 17:
6 CHECK POOR CONTACT.
Check poor contact of auto A/C control module
connector.
B: IN-VEHICLE SENSOR
TROUBLE SYMPTOM:
• Blower fan speed, outlet port and inlet port do not change after turning the AUTO switch to ON
• If the switch LED indicates that the malfunction occurs in sensor, replace the auto A/C control module. The
in-vehicle sensor is built into the auto A/C control module and cannot be replaced as a single unit.
Diagnostic Procedure for Sensors
Is the resistance approximately
2.2 kΩ at 25°C (77°F)?
Is the voltage approx. 5 V?
Is the voltage approx. 5 V?
Is the resistance less than 1 Ω? Go to step 5.
Is the resistance less than 1 Ω? Go to step 6.
Is there poor contact in connec-
tor?
AC(diag)-26
Check Yes
Go to step 2.
Go to step 6.
Go to step 4.
Repair the connec-
tor.
No
Replace the ambi-
ent sensor.
Go to step 3.
Go to step 6.
Repair the open
circuit of the har-
ness between auto
A/C control module
and ambient sen-
sor.
Repair the open
circuit of the har-
ness between auto
A/C control module
and ambient sen-
sor.
Replace the auto
A/C control mod-
ule.