Subaru IMPREZA GD 2007 Series Manual page 3893

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HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)
Step
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 the evaporator sensor.
Terminals
No. 1 — No. 2:
2 CHECK INPUT SIGNAL FOR EVAPORATOR
SENSOR.
1) Turn the ignition switch to ON.
2) Measure the voltage between connector
(B256) terminal and chassis ground.
Connector & terminal
(B256) No. 2 (+) — Chassis ground (–):
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) Turn the ignition switch to ON.
4) Measure the voltage between connector
terminals of auto A/C control module.
Connector & terminal
(B283) No. 7 (+) — No. 17 (–):
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
(B256) No. 2 — (B283) No. 7:
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
(B256) No. 1 — (B283) No. 17:
6 CHECK POOR CONTACT.
Check poor contact of auto A/C control module
connector.
Diagnostic Procedure for Sensors
Is the resistance approximately
3.3 kΩ at 20°C (68°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)-28
Check Yes
Go to step 2.
Go to step 6.
Go to step 4.
Repair the connec-
tor.
No
Replace the evap-
orator sensor.
Go to step 3.
Go to step 6.
Repair the open
circuit of harness
between auto A/C
control module and
evaporator sensor.
Repair the open
circuit of harness
between auto A/C
control module and
evaporator sensor.
Replace the auto
A/C control mod-
ule.