Subaru 2009 IMPREZA Service Manual page 2745

HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)
Step
3 CHECK BLOWER MOTOR RELAY.
1) Turn the ignition switch to OFF.
2) Connect the battery positive terminal to the
blower motor relay terminal No. 2, and the neg-
ative terminal to No. 4.
3) Using the tester, measure the resistance
between terminals.
Connector & terminal
(Relay) No. 1 — No. 5:
4 CHECK HARNESS.
1) Remove the auto A/C control module.
2) Measure the resistance between auto A/C
control module and relay using a tester.
Connector & terminal
(B386) No. 4 — (i88) No. 9:
5 CHECK BLOWER MOTOR POWER SUPPLY.
1) Install the blower motor relay and auto A/C
control module.
2) Turn the ignition switch to ON.
3) Turn the blower fan switch to ON.
4) Use a tester to measure the voltage
between the blower motor and chassis ground.
Connector & terminal
(B87) No. 2 (+) — Chassis ground (–):
6 CHECK BLOWER MOTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from blower
motor.
3) Connect the battery positive terminal to the
blower motor connector terminal No. 2, and the
negative terminal to No. 1.
4) Make sure the blower motor runs.
7 CHECK HARNESS.
1) Disconnect the power transistor connector.
2) Disconnect the auto A/C control module
connector.
3) Using the tester, measure the resistance
between terminals of harness.
Connector & terminal
(B57) No. 1 — Chassis ground:
(B57) No. 2 — (i88) No. 40:
(B57) No. 3 — (B87) No. 1:
(B57) No. 4 — (B87) No. 2:
(B57) No. 4 — (B386) No. 5:
8 CHECK FAN CONTROL SIGNAL.
1) Connect the disconnected connectors.
2) Turn the ignition switch to ON.
3) Change the fan speed control dial from 1st
to 7th.
4) Measure the voltage between the power
transistor and chassis ground using a tester.
Connector & terminal
(B57) No. 2 (+) — Chassis ground (–):
9 CHECK POOR CONTACT.
Check poor contact of auto A/C control module
connector.
Diagnostics for A/C System Malfunction
Is the resistance less than 1 ? Go to step 4.
Is the resistance less than 1 ? Go to step 5.
Is the voltage 10 V or more?
Does the blower motor run?
Is the resistance less than 1 ? Go to step 8.
Is the voltage approx. 10 V at
1st and approx. 1 V at 7th?
Is there poor contact of connec-
tor?
AC(diag)-16
Check Yes
Go to step 6.
Go to step 7.
Replace the power
transistor. <Ref. to
AC-29, REMOVAL,
Power Transistor
(Auto A/C Model).>
Repair the connec-
tor.
No
Replace the blower
motor relay.
Repair or replace
the harness.
Repair or replace
the harness
between relay and
the blower motor.
Replace the blower
motor. <Ref. to AC-
28, REMOVAL,
Blower Motor.>
Repair or replace
the harness.
Go to step 9.
Replace the auto
A/C control mod-
ule. <Ref. to AC-
33, REMOVAL,
Control Unit (Auto
A/C Model).>