Coolant Temperature Indicator
The temperature indicator is controlled by a thermal switch that senses coolant temperature. With ignition switch in "START" position, temperature indicator should come on as a test of indicator bulb. When engine coolant temperature reaches about 258°F (126°C), engine sending unit will close and complete indicator ground circuit, allowing temperature indicator light to come on.
NOTE:
If weak coolant or water only is used in cooling system, indicator light may not come on when boiling point is reached.