Engine Coolant Temperature (ECT) Gage

The pointer of the Engine Coolant Temperature (ECT) Gage is moved by the magnetic fields of two coils. The coils are at right angles to each other. Voltage is applied to coil H from the IG Fuse. The circuit divides at the opposite (ground) side of the coil. One path seeks a ground through coil C and the other path seeks a ground through the variable resistor in the ECT Sending Unit.

When ECT is low, resistance in the ECT Sending Unit is high. Since current will always seek the path of least resistance, current will flow through the H coil and the C coil to ground at G105. Because the length of the C coil winding is twice the length of the H coil winding, the magnetic field generated by coil C is twice as strong as the magnetic field generated by coil H. Therefore, the pointer will be pulled to the "C" position.

As ECT increases, resistance in the ECT Sending Unit decreases. Since current will always seek the path of least resistance, more current will begin to bypass the C coil and travel directly to ground through the ECT Sending Unit. Under these conditions, the coil H magnetic field becomes stronger than the coil C magnetic field and the pointer moves toward the "H" position.