Nissan 240SX/Altima 1993-1998 Repair Guide

Cooling Fan

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TESTING



Electric Fan

See Figure 1



Click image to see an enlarged view

Fig. Fig. 1: Pay special attention to the electric cooling fans when servicing a running engine (or one that is off, but still warm)

These vehicles use two-speed cooling fan circuits. Test the lower speed function first, then the high speed function.

LOW SPEED FUNCTION
  1. Perform a complete visual inspection of all wires and components. Repair wires and replace physically damaged components as necessary.
  2.  
  3. Start the engine and, with the temperature lever at full COLD, turn the air conditioner and blower fan switches ON .
  4.  
  5. Run the engine at idle for a few minutes with the air conditioning operating and ensure that the cooling fan operates at low speed.
  6.  
  7. If the cooling fan does not operate at low speed, inspect the low speed cooling fan circuit.
  8.  
  9. Turn the ignition switch OFF and disconnect the cooling fan motor electrical harness.
  10.  
  11. Check continuity between terminals 1 and 5. Continuity should exist. If continuity does not exist, check for a short circuit in the harness.
  12.  
  13. Check continuity between terminals 4 and ground. Continuity should exist. If continuity does not exist, check for a short circuit in the harness.
  14.  
  15. Disconnect the ECM harness and check continuity between ECM terminals 14 and 2. Continuity should exist. If continuity does not exist, check for a short circuit in the harness.
  16.  
  17. Apply power and ground to the cooling fan motors. The motors should operate. If the motors do not operate properly, the cooling fans are faulty. If the motors operate properly, the cooling fan relay may be defective.
  18.  

HIGH SPEED FUNCTION
  1. Perform a complete visual inspection of all wires and components. Repair wires and replace physically damaged components as necessary.
  2.  
  3. Turn the air conditioner switch OFF .
  4.  
  5. Disconnect the engine coolant temperature sensor harness and attach a 150 ohm resistor (available at most electronics stores) to the harness connector terminals.
  6.  
  7. Start the engine. If the cooling fan does not operate at high speed, inspect the high speed cooling fan circuit.
  8.  
  9. Check the cooling system for leaks. Low cooling system volume may cause the coolant temperature sensor to read incorrectly. Repair leaks as necessary.
  10.  
  11. Check the radiator cap with a pressure tester. Replace the radiator cap as necessary.
  12.  
  13. Check the thermostat for proper operation. Incorrect thermostat operation affects coolant temperature sensor operation. Replace the thermostat as necessary.
  14.  
  15. Inspect the coolant temperature sensor for proper operation. Refer to Coolant Temperature Sensor testing in Driveability & Emissions Controls of this repair guide. Replace the coolant temperature sensor as necessary.
  16.  

REMOVAL & INSTALLATION



Mechanical Fan
  1. Disconnect the negative battery cable.
  2.  
  3. Loosen the fan pulley attaching bolts, but do not remove.
  4.  
  5. Remove the accessory drive belts.
  6.  
  7. Remove the fan shroud, as necessary to gain clearance.
  8.  

Take care to not allow the fan to contact the radiator. The radiator fins are easily damaged.

  1. Remove the fan pulley attaching bolts and carefully remove the fan from the engine.
  2.  

To install:
  1. Install the fan pulley and hand-tighten the attaching bolts.
  2.  
  3. Install the fan shroud, if removed.
  4.  
  5. Install and tension the accessory drive belts.
  6.  
  7. Final-tighten the fan attaching bolts to 56-66 inch lbs. (6-8 Nm).
  8.  
  9. Re-tension the accessory drive belts, as necessary.
  10.  
  11. Connect the negative battery cable.
  12.  

Electric Fan

See Figures 2 and 3



Click image to see an enlarged view

Fig. Fig. 2: When removing the engine fan assembly, disconnect the electrical harnesses (lower arrows) and remove the mounting bolts (upper arrows)



Click image to see an enlarged view

Fig. Fig. 3: The fan electrical harness is attached to the shroud with a special clip (arrow). Working carefully, the clip can be opened using a pick

  1. Disconnect the negative battery cable.
  2.  
  3. Drain and recycle the engine coolant.
  4.  
  5. Disconnect the upper radiator hose from the radiator and lay it aside.
  6.  
  7. Label and disconnect the cooling fan electrical harnesses.
  8.  
  9. Remove the bolts securing the fan shroud assembly to the radiator.
  10.  
  11. Remove the cooling fan and shroud assembly from the vehicle.
  12.  

To install:
  1. Install the cooling fan and shroud assembly. Tighten the fan shroud mounting bolts to 29-37 inch lbs. (3-4 Nm) on Altima and 34-40 inch lbs. (4-5 Nm) on 240SX.
  2.  
  3. Install the upper radiator hose and tighten the clamp securely.
  4.  
  5. Refill and bleed the cooling system.
  6.  
  7. Connect the cooling fan electrical harnesses.
  8.  
  9. Connect the negative battery cable.
  10.  
  11. Start the engine and check for leaks.
  12.  
  13. Verify the operation of the cooling fans.
  14.  

 
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