Temperature Warning Lamp/Indicator: Testing and Inspection

If the red light is not lit when engine is being cranked, check for a burned out bulb, open in light circuit, or a defective ignition switch.
If red light is lit when engine is running, check wiring between light and switch for a ground, defective temperature switch, or overheated cooling system. As a test circuit to check whether the red bulb is functioning properly, a wire which is connected to the ground terminal of the ignition switch is tapped into its circuit. When the ignition is in ``Start'' (engine cranking) position, ground terminal is grounded inside the switch and the red bulb will be lit. When engine is started and the ignition switch is in the On position, test circuit is opened and bulb is then controlled by the temperature switch.