Subaru Impreza 2002 Service Manual page 3233

HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)
Step
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 temperature control dial to maximum
cold position.
3)Measure the voltage between magnet clutch
connector and chassis ground.
Connector & terminal
(F24) No. 3 (+) — Chassis ground ( − − − − ):
3 CHECK SIGNAL VOLTAGE TO A/C RELAY.
1)Turn the ignition switch to ON.
2)Turn the A/C switch to ON.
3)Measure the signal voltage to A/C relay and
chassis ground.
Connector & terminal
(F31) No. 9 (+) — Chassis ground ( − − − − ):
4 CHECK A/C RELAY.
1)Remove the A/C relay in main fuse box.
2)Check the A/C relay. <Ref. to AC-38,
INSPECTION, Relay and Fuse.>
5 CHECK OPERATION OF MAIN FAN MOTOR.
1)Start the engine.
2)Turn the A/C switch to ON.
3)Check the operation of main fan motor.
6 CHECK POWER SUPPLY TO MAIN FAN MO-
TOR.
CAUTION:
Be careful not to overheat the engine during
repair.
1)Turn the ignition switch to OFF.
2)Disconnect the 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 the voltage between main fan
motor connector and chassis ground.
Connector & terminal
Turbo engine model:
(F17) No. 2, 3 (+) — Chassis ground ( − − − − ):
Non-turbo engine model:
(F17) No. 2 (+) — Chassis ground ( − − − − ):
7 CHECK GROUND CIRCUIT OF MAIN FAN
MOTOR.
1)Turn the ignition switch to OFF.
2)Measure the resistance between main fan
motor connector and chassis ground.
Connector & terminal
(F17) No. 1 — Chassis ground:
8 CHECK POOR CONTACT.
Check poor contact in main fan motor connec-
tor.
DIAGNOSTICS FOR A/C SYSTEM FAILURE
Check
Is the voltage more than 10 V? Go to step 3.
Is the voltage more than 10 V? Go to step 4.
Is the operation of the relay
OK?
Does the radiator main fan
operate?
Is the voltage more than 10 V? Go to step 7.
Is the resistance less than 1
Ω?
Is there poor contact in main
fan motor connector?
AC-28
Yes
Repair the open
circuit in harness
for power supply
line of the A/C
compressor.
Repair the open
circuit in harness
for power supply
line.
Go to step 5. Replace the A/C
relay.
Go to step 10. Go to step 6.
Repair the open
circuit in harness
for power supply
circuit.
Go to step 8. Repair the open
circuit in harness
between main fan
motor connector
and chassis
ground.
Repair the poor Go to step 9.
contact in main fan
motor connector.
No