High Coolant Temperature Warning

The diesel engine's coolant temperature gauge uses an overheat switch that closes at approximately 116°C (241°F) that will illuminate the engine warning indicator.

Water Temperature Indicator Sender Unit

When the engine coolant temperature is low, the resistance of the engine coolant temperature sender unit is high, restricting the flow of current through the gauge, and moving the pointer only a short distance. As the coolant temperature increases, the resistance of the engine coolant temperature sender unit decreases, causing a proportionately increased flow of current through the engine coolant temperature sender unit and a corresponding movement of the pointer.