Engine Coolant Temperature Gauge

The pointer of the ECT gauge is moved by the magnetic fields of two coils (H and C). The coils are at right angles to each other. Voltage is applied to the H coil from the gauge fuse, located in junction block 2, when the ignition is in the ON or START positions. Current flows from the gauge fuse to junction block 3, via the RED/BLU wire between the junction Block 2, C2 cavity 9 and the junction block 3, C3 cavity 5. Current flows to the instrument cluster assembly C1 cavity 2 from the junction block 3, C2 cavity 18. The circuit divides at the opposite side of the coil, this side is attached to ground. One path seeks a ground through coil C and the other path seeks a ground through the variable resistor in the ECT sender unit.

When ECT gauge 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. Since the length of the C coil is twice the length of the H coil winding, the magnetic field generated by coil C is twice as strong as the magnetic field by coil H. Therefore the pointer will be pulled to the C position.

As the ECT temperature increases, resistance in the ECT sending unit decreases. Since current flows to 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 towards the H position.