Subaru Legacy 2003 Service Manual page 3519

DIAGNOSTICS FOR A/C SYSTEM FAILURE (RHD MODEL)
HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)
1 CHECK FUSE.
1) Turn ignition switch to OFF.
2) Remove No. 2 fuse in main fuse box.
3) Check condition of fuse.
Is the fuse blown-out?
2 CHECK POWER SUPPLY TO MAGNET
CLUTCH OF A/C COMPRESSOR.
1) Start the engine, and turn A/C switch to
ON.
2) Set the compartment temperature at 18°C
(65°F) (FULL COOL).
3) Measure voltage between magnet clutch
connector and chassis ground.
Connector & terminal
(F24) No. 1 (+) — Chassis ground ( − − − − ):
Does the measured value exceed the spec-
ified value?
3 CHECK SIGNAL VOLTAGE FROM A/C RE-
LAY.
1) Turn ignition switch to ON.
2) Turn A/C switch to ON.
3) Measure voltage between A/C relay and
chassis ground.
Connector & terminal
(F31) No. 10 (+) — Chassis ground ( − − − − ):
Does the measured value exceed the spec-
ified value?
4 CHECK A/C RELAY.
1) Remove A/C relay in main fuse box.
2) Check A/C relay. <Ref. to AC-44, INSPEC-
TION, Relay and Fuse.>
Is the operation of relay OK?
5 CHECK OPERATION OF MAIN FAN MOTOR.
1) Start the engine.
2) Turn A/C switch to ON.
3) Check operation of main fan motor.
Does the main fan operate?
6 CHECK POWER SUPPLY TO MAIN FAN MO-
TOR.
CAUTION:
Be careful not to overheat engine during re-
pair.
1) Turn ignition switch to OFF.
2) Disconnect connector from main fan motor.
3) Start the engine, and warm it up until
engine coolant temperature increases over
95°C (203°F).
4) Stop the engine and turn ignition switch to
ON.
5) Measure voltage between main fan motor
connector and chassis ground.
Connector & terminal
4 CYLINDER MODEL
(F17) No. 2 (+) — Chassis ground ( − − − − ):
6 CYLINDER MODEL
(F17) No. 1, 2, 3 (+) — Chassis ground
( − − − − ):
Does the measured value exceed the spec-
ified value?
Step Value
Fuse is not blown.
10 V
10 V
Operation of each relay is OK. Go to step 5.
Main fan motor operates.
10 V
AC-46
Yes
Go to step 2. Replace fuse.
Go to step 3. Repair harness for
power supply line
of the A/C com-
pressor.
Go to step 4. Repair harness for
power supply line.
Replace A/C relay.
Go to step 10. Go to step 6.
Go to step 7. Repair harness for
power supply cir-
cuit.
No