Temperature Warning Lamp/Indicator: Description and Operation

The engine coolant temperature lamp comes on to warn the driver of high coolant temperature. With the ignition switch is in the RUN or START position the voltage from the fuse block is applied to the lamp. In the START position the lamp circuit receives ground through the ignition switch so that the bulb can be tested. In the RUN position current through the bulb can be grounded through the coolant temperature switch.