Engine Coolant Temperature Gauge (ECT)

The pointer of the ECT gauge is moved by the magnetic fields of two coils. The coils are at right angles to each other. The voltage is applied to coil H from the IG-COIL fuse. The circuit divides at the opposite (ground) side of the coil. One path seeks a ground through coil C. The other path seeks a ground through the variable resistor in the Engine Coolant Temperature (ECT) Sensor.

When the engine coolant temperature (ECT) is low, the resistance in the ECT sensor is high. Because the current always seeks the path of least resistance, the current flows through the H coil and the C coil to ground at G 105. Because the length of the C coil winding is twice the length of the H coil winding, the magnetic field generated by the coil C is twice as strong as the magnetic field generated by the coil H. Therefore, the pointer may be pulled to the C position.

As the ECT increases, the resistance in the ECT sensor decreases. Because the current always seeks the path of least resistance, more current begins to bypass the C coil, traveling directly to the ground through the ECT sensor. Under these conditions, the coil H magnetic field becomes stronger than the coil C magnetic field. The pointer moves toward the H position.