See Figures 1 and 2
When coolant temperature is low, the resistance of the sending unit is high, restricting the flow of current through the gauge and moving the pointer only a short distance. As coolant temperature rises, the resistance of the sending unit decreases, causing a proportional increase in current flow through the sending unit and corresponding movement of the gauge pointer.
The sending unit may only be tested for operation. There is no calibration, adjustment or maintenance required.
- Disconnect the sending unit electrical harness.
- Remove the radiator cap and place a mechanic's thermometer in the coolant.
- Using an ohmmeter, check the resistance between the sending unit terminals.
- Resistance should be high (375 ohms) with engine coolant cold and low (180 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.
- If resistance does not drop as engine temperature rises, the sending unit is faulty.
REMOVAL & INSTALLATION
- Disconnect the negative battery cable.
- Drain the cooling system into a suitable container.
- Disengage the electrical connector at the temperature sender/switch.
- Remove the temperature sender/switch.
- Apply pipe sealant or Teflon® tape to the threads of the new sender/switch. Tighten it to 8-18 ft. lbs. (11-24 Nm).
- Install the temperature sender/switch and connect the electrical connector.
- Connect the negative battery cable. Fill the cooling system.
- Run the engine and check for leaks.