Subaru Legacy 2004 Service Manual page 3433

Step
1 CHECK FUSE.
1) Turn the ignition switch to OFF.
2) Remove the fuse No. 22 from fuse & relay
box.
3) Check the condition of fuse.
2 CHECK SIGNAL TO A/C RELAY AND A/C
CONTROL MODULE.
1) Disconnect the A/C relay and auto A/C con-
trol module harness connector.
2) Turn the ignition switch to ON.
3) Measure the voltage between A/C relay
connector terminal and chassis ground.
4) Measure the voltage between auto A/C
control module harness connector terminal
and chassis ground.
Connector & terminal
(F27) No. 31 (+) — Chassis ground (
(B282) No. 10 (+) — Chassis ground (
3 CHECK POWER SUPPLY FOR PRESSURE
SWITCH.
1) Turn the ignition switch to OFF.
2) Disconnect the pressure switch harness
connector.
3) Turn the ignition switch to ON.
4) Measure the voltage between pressure
switch harness connector terminal and chassis
ground.
Connector & terminal
(B10) No. 2 (+) — Chassis ground (
4 CHECK HARNESS BETWEEN PRESSURE
SWITCH AND A/C RELAY, AUTO A/C CON-
TROL MODULE.
1) Turn the ignition switch to OFF.
2) Measure the resistance in harness
between pressure switch connector and A/C
relay connector.
3) Measure the resistance in harness
between pressure switch connector and auto
A/C control module connector.
Connector & terminal
(B10) No. 1 — (F27) No. 31:
(B10) No. 1 — (B282) No. 10:
5 CHECK POWER SUPPLY FOR A/C RELAY.
Measure the voltage between A/C relay con-
nector terminal and chassis ground.
Connector & terminal
(F27) No. 28 (+) — Chassis ground (
6 CHECK A/C RELAY.
Check the A/C relay. <Ref. to AC-39, INSPEC-
TION, Relay and Fuse.>
Diagnostics for A/C System Malfunction
Is the fuse blown-out?
Is the voltage more than 10 V? Go to step 5.
$
):
$
):
Is the voltage more than 10 V? Go to step 4.
$
):
Is the resistance less than 1
#?
Is the voltage more than 10 V? Go to step 6.
$
):
Is malfunction found in A/C
relay?
AC(diag)-21
HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)
Check Yes
Replace the fuse.
Check the pres-
sure switch. <Ref.
to AC-40,
INSPECTION,
Pressure Switch
(Triple Pressure
Switch).>
Go to step 7.
No
Go to step 2.
Go to step 3.
Check the harness
for open or short
circuit between
fuse and pressure
switch.
Repair the har-
ness.
Check the harness
for open or short
circuit between
fuse and A/C relay.
Replace the A/C
relay.