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Home >> Volvo >> 1995 >> 850 L5-2.4L VIN 55 B5254S >> Repair and Diagnosis >> Powertrain Management >> Computers and Control Systems >> Testing and Inspection >> Component Tests and General Diagnostics >> Other Electrical Fault Tracing >> Checking the Engine Cooling Fan >> With Standard Transmission

With Standard Transmission

CHECKING ENGINE COOLING FAN





Conditions for Fault Tracing:
^ No DTCs present.
^ Fault is permanent.

Fault Sources:
^ Engine cooling fan runs continuously at half speed:
- Half-speed signal lead short-circuited to ground.
- Faulty fan relay.

^ Engine cooling fan runs continuously at full speed:
- Full-speed signal lead short-circuited to ground.
- Faulty fan relay.

^ Engine cooling fan does not operate at half speed:
- Open-circuit in half-speed signal lead.
- Faulty fan or fan relay.

^ Engine cooling fan does not operate at full speed:
- Open-circuit in full-speed signal lead.
- Faulty fan or fan relay.

^ Engine cooling fan does not operate at either half or full speed:
- Open-circuit in supply lead or ground lead.
- Faulty fan or fan relay.

TESTING PROCEDURE

Fault Symptoms
^ If engine cooling fan RUNS continuously at half speed, even when ignition is OFF:
- Proceed to: Checking Fan Relay, Half Speed, section below.

^ If engine cooling fan RUNS continuously at full speed, even when ignition is OFF:
- Proceed to: Checking Fan Relay, Full Speed, section below.

^ If neither of above symptoms is present:
- Proceed to: Functional Test of Engine Cooling Fan, section below.





Functional Test of Engine Cooling Fan
^ Activate Ignition System Diagnostic Test Mode 3 and check that engine cooling fan RUNS at low and high speed.

See: COMPUTERS AND CONTROL SYSTEMS / TESTING AND INSPECTION / OUTPUT DEVICE TEST - DIAGNOSTIC TEST MODE 3 / IGNITION SYSTEM.

If fan runs at both speeds:
- Fault is intermittent.
If fan runs at half speed only:
- Proceed to: Checking Full-Speed Signal Lead.
If fan runs at full speed only:
- Proceed to: Checking Low-Speed Signal Lead, section below.
If fan fails to run:
- Proceed to: Checking Supply Lead to Fan Relay, section below.





Checking Full-Speed Signal Lead
^ Switch OFF Ignition.
^ Connect test box to Distributor Ignition (DI) System and check ground terminals.
^ Disconnect connector B from Cooling Fan (FC) Relay.
^ Connect ohmmeter between #26 (ICM A26) on test box and fan relay connector B, terminal 2.

Instrument should indicate approx. 0 Ohms.

If reading is correct:
- Proceed to: Checking Fan Motor, Full Speed.
If resistance is infinite:
- Check lead between ICM A26 and fan relay terminal 2B for open-circuit.





Checking Fan Motor, Full Speed
^ Switch OFF Ignition.
^ Disconnect fan relay connector C
^ Connect ohmmeter between connector C terminal 2 and ground.

Instrument should indicate 0 - 10 Ohms.

If reading is correct:
- Try with new fan relay.
If reading is incorrect:
- Try with new engine cooling fan.





Checking Low Speed Signal Lead
^ Switch OFF Ignition.
^ Connect test box to DI system and check ground terminals.
^ Disconnect fan relay connector B.
^ Connect ohmmeter between #17 ( ICM A17) on test box and fan relay connector B, terminal 1.

Instrument should indicate approx. 0 Ohms.

If reading is correct:
- Proceed to: Checking Fan Motor, Low Speed.
If resistance is infinite:
- Check lead between ICM A17 and fan relay terminal B1 for open-circuit.





Checking Fan Motor, Low Speed
^ Switch OFF Ignition.
^ Disconnect fan relay connector C.
^ Connect ohmmeter between connector C terminal 1 and ground.

Instrument should indicate 0 - 10 Ohms.

If reading is correct:
- Try with new fan relay.
If reading is incorrect:
- Try with new engine cooling fan.





Checking Supply Lead to Fan Relay
^ Switch OFF Ignition.
^ Disconnect fan relay connector A.
^ Connect voltmeter between connector A and ground.

Instrument should indicate battery voltage.

If reading is correct:
- Proceed to: Checking ground lead.
If voltage is approx. 0 Volts:
- Lead between starter motor and relay incorporates a fuse. Open circuit in this lead will probably be due to short-circuit to ground in circuit. Therefore, check relay and fan motor before replacing lead. Check lead between starter motor and fan relay terminal A1 for open circuit.





Checking Ground Lead
^ Switch OFF Ignition.
^ Disconnect ground lead single-pin connector (C/EA).
^ Connect ohmmeter between single-pin connector (on body side) and ground.

Instrument should indicate approx. 0 Ohms.

If reading is correct:
- Proceed to: Checking fan motor.
If reading is incorrect:
- Check ground terminal for contact resistance and oxidation.
- Check lead between fan motor and ground for open-circuit.





Checking Fan Motor
^ Switch OFF Ignition.
^ Reconnect ground lead single-pin connector.
^ Disconnect fan relay connector C.
^ Connect ohmmeter between connector C terminal 2 and ground.

Instrument should indicate 0 - 10 Ohms.

If reading is correct:
- Try with new relay.
If reading is incorrect:
- Try with new engine cooling fan.





Checking Fan Relay, Half Speed
^ Switch OFF Ignition.
^ Disconnect fan relay connector B.

If engine cooling fan stops:
- Check lead between ICM A17 and fan relay terminal B1 for short-circuit to ground.
If engine cooling fan does not stop:
- Try with new relay.





Checking Fan Relay, High Speed
^ Switch OFF Ignition.
^ Disconnect fan relay connector B.

If engine cooling fan stops:
- Check lead between ICM A26 and relay terminal B2 for short circuit to ground.
If engine cooling fan does not stop:
- Try with new relay.

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