Chrysler Full-Size Trucks 1997-2000 Repair Guide

Coolant Temperature Gauge Sending Unit

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The temperature gauge sending unit controls the gauge or warning light. Some models use two temperature sensors (one for the gauge or warning light and one as a PCM input), which may be located adjacent to each other. Refer to the illustrations.

REMOVAL & INSTALLATION



  1. The engine should be cold when performing this procedure.
  2.  
  3. Disconnect the battery negative cable.
  4.  
  5. Drain engine coolant to below sending unit level. A quart or so should be sufficient.
  6.  
  7. Disconnect the wiring from the temperature gauge sending unit.
  8.  
  9. Unscrew the old sending unit.
  10.  

To install:

  1. Coat the threads of the new unit with Teflon®tape or a temperature-resistant sealer.
  2.  
  3. Tighten the sensor to 11-15 ft lbs. (15-20 Nm).
  4.  
  5. Reconnect wiring. Start the engine and check operation. Check for leaks at operating temperature.
  6.  



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Fig. Coolant temperature sensor-typical



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Fig. Coolant temperature sensor on the 2.5L engine is in the thermostat housing



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Fig. On 3.9L, 5.2L and 5.9L gas engines, the coolant temperature sensor is just behind the



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Fig. Coolant temperature sensor position on the 4.7L engine



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Fig. Coolant temperature sensor location-8.0L engine



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Fig. Coolant temperature sensor-5.9L diesel engine

TESTING



  1. The sending unit varies the resistance of the circuit in response to changes in coolant temperature. With a cold engine, resistance is high and gauge reading is low or the warning light is OFF. When the engine is hot, resistance is low and the gauge reading is high or the warning light is ON.
  2.  
  3. Disconnect the wiring to the sending unit and connect a jumper across the two leads. When the ignition is turned on, the gauge needle should move to the maximum or the warning light will go ON. If this happens, the gauge or light is functioning properly and the problem is likely to be the sensor.
  4.  
  5. If an ohmmeter is available, connect it across the sending unit terminals and start the engine. Resistance should decrease as the coolant temperature increases. If it does not, replace the sending unit.
  6.  

 
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