Temperature Gauge: Description and Operation

The engine coolant temperature gauge consists of two intersecting coils wound around a permanent magnet rotor. When voltage through fuse C-10 is applied to the coils, a magnetic field is generated. This causes the rotor to rotate and the gauge needle to move. The magnetic field is controlled by the engine coolant temperature sending unit. As the resistance in the sending unit varies, current through the gauge coils changes, and the gauge needle moves according to the changing magnetic field. See the chart below for approximate resistance values for the sending unit under normal operating conditions.

Engine Coolant Temperature Engine Coolant Temperature Sending Unit's Resistance
140° F/60° C 160 Ohms
150° F/66° C 135 Ohms
160° F/71° C 110 Ohms
170° F/77° C 90 Ohms
180° F/82° C 75 Ohms
190° F/88° C 60 Ohms