Expedition, Navigator 2006-2007



  1. Check the appropriate fuse before attempting any other diagnostics.
  3. Disconnect the sending unit electrical harness.
    Never open, service or drain the radiator or cooling system when hot; serious burns can occur from the steam and hot coolant. Also, when draining engine coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze and could drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantities. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.

  5. Remove the radiator cap and place a mechanic-s thermometer in the coolant.
  7. Using an ohmmeter, check the resistance between the sending unit terminals.
  9. Resistance should be high (74 ohms) with engine coolant cold and low (9.7 ohms) with engine coolant hot.
    It is best to check resistance with the engine cool, then start the engine and watch the resistance change as the engine warms.

  11. If resistance does not drop as engine temperature rises, the sending unit is faulty.

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Fig. Cylinder Head Temperature Sensor connector

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Fig. CHT Resistance Values Chart

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Fig. CHT Voltage Chart

  1. Checking the resistance of the CHT sensor:

    The vehicle must be at normal operating temperature.
    Turn the ignition switch off.
    Disconnect the CHT sensor electrical connector.
    Measure the resistance between Pin 1 (CHT+) and Pin 2 (SIGRTN -) on component side.
    Refer to the chart at the beginning of this test for resistance specifications.