Jeep Wagoneer/Commando/Cherokee 1984-1998

Coolant Temperature Sender

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TESTING



Perform this test on a cold or cool engine.

  1. Disconnect the negative (-) battery cable.
  2.  
  3. Unplug the electrical wiring from the sending unit.
  4.  
  5. Using an ohmmeter, measure the resistance between the terminal and the sending unit's metal body
    1. Infinite resistance or zero resistance: the sending unit is bad, replace the sender with a new one.
    2.  
    3. Other than infinite or zero resistance: continue test.
    4.  

  6.  
  7. Remove the temperature sender from the engine.
  8.  
  9. Position the sending unit so the metal shaft (opposite end from the electrical connectors) is in a pot of water. Make sure that the electrical connector is not submerged and only the tip of the sending unit's body is in the water.
  10.  
  11. Heat the pot of water at a medium rate. While the water is warming, continue to measure the resistance of the terminal and the metal body of the sending unit:
    1. As the water warms up, the resistance goes down in a steady manner: the sending unit is good.
    2.  
    3. As the water warms up, the resistance does not change or changes in erratic jumps: the sender is bad, replace it with a new one.
    4.  

  12.  
  13. Install the good or new sending unit into the engine, then connect the negative battery cable.
  14.  

Removal & Installation



See Figure 1



Click image to see an enlarged view

Fig. Fig. 1: Coolant temperature sensor location-4.0L model shown, others similar


CAUTION
When draining the coolant, keep in mind that cats and dogs are attracted by ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old.

  1. Disconnect the negative battery cable.
  2.  
  3. Drain the cooling system to a level is below the sensor.
  4.  
  5. Detach the electrical connector from the sensor.
  6.  
  7. Remove the sensor from the engine. On some applications, the coolant sensor threads into the thermostat housing.
  8.  
  9. Installation is the reverse of the removal procedure. Fill and bleed the cooling system.
  10.  

 
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