Temperature Warning Lamp/Indicator: Description and Operation

Bimetal Type

The temperature lamp system provides the driver with an indication of engine coolant temperature by means of a switch mounted in the intake manifold and a red engine lamp mounted on the instrument panel. The temperature switch has a temperature sensitive bimetallic arm which completes the lamp circuit through the switch to engine ground.

Magnetic Type

The temperature indicating system is a magnetic type system, which consists only of the sending unit located in the engine block or cylinder head and a temperature gauge in the instrument cluster. The sending unit changes resistance according to the temperature of engine coolant, which varies the current flow through the gauge. The pointer position varies proportionally to the current flow. The sender resistance is high when coolant temperature is low, and low when coolant temperature is high.
The pointer of the magnetic gauge remains in position when ignition is turned to the Off position. It will move to the correct indication whenever the ignition is turned back to On position.