Temperature Gauge: Description and Operation

When the ignition switch is in ON (II) or START (III), battery voltage is supplied through fuse 15 to the gauges in the gauge assembly.

The Engine Coolant Temperature (ECT) gauge has two intersecting coils wound around a permanent magnet 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 engine coolant temperature (ECT) sending unit's resistance varies from about 137 ohms at low engine temperature to between 3O-46 ohms at high temperature (radiator fan running).