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Home >> Infiniti >> 2000 >> G20 Base, Automatic, RE4F03B >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> HVAC Control Systems >> Manual A/C-Heater Systems >> System Tests >> Radiator Fan Circuits >> Radiator Fan Control

Radiator Fan Control

  1. Check for proper level of coolant in cooling system. Start engine. Turn A/C and blower on. Set controls for maximum cooling. Idle engine for several minutes. If fans operate at low speed, go to next step. If fans do not operate, go to step  3.
  2. Turn A/C and blower off. Turn ignition off. Disconnect connector from engine coolant sensor. See Fig 1. Connect 150-ohm resistor across coolant sensor harness connector terminals. Start engine. If fans run at high speed, fan circuits are okay. If fans do not run at high speed, go to next step.
  3. Stop engine. Remove radiator fan relays No. 2 and 3 from relay box located at right side of engine compartment. Start engine. Turn A/C and blower on. Set controls for maximum cooling. Idle engine for several minutes. If fans operate at low speed, go to next step. If fans do not operate, go to step  6.
  4. Turn ignition off. Reinstall radiator fan relays No. 2 and 3. Remove cooling fan relay No. 1 from relay box located at right side of engine compartment. Turn A/C and blower off. Disconnect connector from engine coolant sensor. See Fig 1. Connect 150-ohm resistor across coolant sensor harness connector terminals. Start engine. If fans run at high speed, fan circuits are okay. If fans do not run at high speed, go to step  11.
  5. Check cooling system for leaks. Check radiator cap and thermostat for proper operation. Repair or replace as necessary. If system is functioning properly, remove Engine Coolant Temperature (ECT) sensor. See Fig 1. Place ECT sensor in a container of hot water. Using ohmmeter, measure resistance between ECT sensor terminals. See ENGINE COOLANT TEMPERATURE SENSOR SPECIFICATIONS  table. If resistance is not as specified, replace ECT sensor.
  6. Turn ignition off. Remove cooling fan relay No. 1. Turn ignition on. Check voltage between ground and cooling fan relay harness connector terminals No. 1 (Brown wire), No. 3 (Green wire) and No. 7 (Green/White wire). If battery voltage does not exist at each terminal, go to next step. If battery voltage exists at each terminal, go to step  8.
  7. Check fuse No. 16 (10-amp) in fuse block. Fuse block is located at lower left side of instrument panel. Check fusible links "B" (40-amp) and "C" (40-amp). Fusible links are located in fuse and fusible link box next to battery. Also check for open or short in wire harness between cooling fan relay No. 1 and fuse, fusible link or battery. Repair or replace as necessary. See WIRING DIAGRAMS .
  8. Turn ignition off. Disconnect both cooling fan connectors. Check for short or open in Black wire between cooling fan No. 1 (left side of engine compartment) or cooling fan No. 2 (right side of engine compartment) harness connector terminal No. 4 and ground connector terminal located next to hood switch, between strut tower and air cleaner. Check for short or open in Green/Red wire between cooling fan No. 1 harness connector terminal No. 1 and cooling fan relay harness connector terminal No. 6. Check for short or open in Green/Black wire between cooling fan No. 2 harness connector terminal No. 1 and cooling fan relay harness connector terminal No. 5. Repair as necessary. If wires are okay, go to next step.
  9. Disconnect Engine Control Module (ECM) harness connector, located behind center console controls. Check for short or open in Blue/Yellow wire between ECM harness connector terminal No. 14 and radiator fan relay No. 1 harness connector terminal No. 2. Repair as necessary. If wire is okay, go to next step.
  10. Test radiator fan relay No. 1. See RADIATOR FAN RELAYS . Replace relay if defective. If relay is okay, test radiator fans. See RADIATOR FANS . Replace fans if defective. Reconnect all connectors.
  11. Turn ignition off. Remove radiator fan relays No. 2 and 3 from relay box located at right side of engine compartment. Turn ignition on. Check for battery voltage at harness connector terminals No. 1 and 3 at each relay. If battery voltage exists, go to step  13. If battery voltage does not exist, go to next step.
  12. Check for a short or open in Brown wire between cooling fan relays No. 2 or 3, and fuse No. 16 (10-amp). Fuse is located in fuse block at lower left side of instrument panel. Check for short or open in Green wire between cooling fan relay No. 3 and fusible link "B" (40-amp). Check for short or open in Green/White wire between cooling fan relay No. 2 and fusible link "C" (40-amp). Fusible links are located in fuse and fusible link box next to battery.
  13. Turn ignition off. Disconnect fan motor connectors. Test for continuity in Green/Yellow wire between terminal No. 2 of fan motor No. 1 and terminal No. 5 of radiator fan relay No. 2 harness connector. Test for continuity in Light Green/Black wire between terminal No. 3 of fan motor No. 1 and terminal No. 6 of radiator fan relay No. 2 connector. Test for continuity in Black wire between terminal No. 7 of radiator fan relay No. 2 harness connector and ground. If continuity exists at each wire, go to next step. If continuity does not exist at each wire, repair short or open in appropriate wire.
  14. Test for continuity in Green/Yellow wire between terminal No. 2 of fan motor No. 2 and terminal No. 5 of radiator fan relay No. 3 harness connector. Test for continuity in Light Green/Black wire between terminal No. 3 of fan motor No. 2 and terminal No. 6 of radiator fan relay No. 3 connector. Test for continuity in Black wire between terminal No. 7 of radiator fan relay No. 3 harness connector and ground. If continuity exists at each wire, go to next step. If continuity does not exist at each wire, repair short or open in appropriate wire.
  15. Ensure ECM connector is disconnected. Test for short or open in Light Green wire between PCM harness connector terminal No. 13 and terminal No. 2 of harness connector for radiator fan relays No. 2 and 3. If continuity exists, go to next step. If continuity does not exist, repair Light Green wire and circuit connectors.
  16. Test radiator fan relay No. 1. See RADIATOR FAN RELAYS . Replace relay if defective. If relay is okay, test radiator fans. See RADIATOR FANS . Replace fans if defective.
ENGINE COOLANT TEMPERATURE SENSOR SPECIFICATIONS

Temperature - °F (°C) Ohms
68 (20) 2.10-2.90
122 (50) .68-1.00
194 (90) .24-.26
Fig 1: Locating ECT Sensor Harness Connector
G00010199Courtesy of NISSAN MOTOR CO., U.S.A.
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