Temperature Gauge: Description and Operation

The engine coolant temperature gauge has two intersecting coils wound around a permanent magnetic rotor. Voltage applied to the coils, through fuse 15, generates a magnetic field. The magnetic field, controlled by the coolant temperature sending unit, causes the rotor to rotate and the gauge needle to move. As the resistance in the sending unit varies, current through the gauge coils changes. The gauge needle moves toward the coil with the strongest magnetic field. The fuel gauge works the same way.

The Engine Coolant Temperature (ECT) sending unit's resistance varies from about 137 ohms at low engine temperature to between 30-46 ohms at high temperature (radiator fan running).

The fuel gauge sending unit's resistance varies from about 2-5 ohms at full, to about 110 ohms at empty. When the ignition switch is turned to lock (O), the gauge remains at the last reading until you turn the ignition switch to ON (II) or START (III) again.