Subaru Forester 2004 - Page 92

AC-38
HVAC SYSTEM (AUTO A/C)(DIAGNOSTIC)
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. 2.7
kΩ 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
(B256) terminal and chassis ground.
Connector & terminal
(B256) No. 1 (+) — Chassis ground (
− ):
Is the voltage approx. 5 V? Go to step 5. 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
(i49) No. 2 (+) — (i48) No. 16 (
− ):
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
(B256) No. 1 — (i49) No. 2:
Is the resistance less than 1Ω? 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
(B256) No. 3 — (i48) No. 16:
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.