Engine Coolant Temperature Gauge
Needle of Engine Coolant Temperature (ECT) gauge is moved by magnetic fields of 2 coils ("C" and "H"). Coils are at right angles to each other. Voltage is applied to coil "H" from GAUGE fuse (10-amp) when ignition switch is in RUN or START positions. GAUGE fuse (10-amp) is located in instrument panel junction box No. 2. See Fig 1 . Voltage flows from GAUGE fuse (10-amp) instrument panel junction box No. 2 harness connector C2 terminal No. 9, through Red/Blue wire, to junction block No. 3 harness connector C3 terminal No. 5. See Fig 2 and Fig 3 . Voltage flows to instrument cluster assembly C1 terminal No. 2 from junction block No. 3 harness connector C2 terminal No. 18 (Red/Blue wire). Circuit divides at opposite side of coil, this side is attached to ground. One path seeks a ground through coil "C" and other path seeks ground through variable resistor in ECT sending unit. When ECT gauge is low, resistance in ECT sending unit is high. Since voltage will always seek path of least resistance, voltage will flow through coil "H" and coil "C" to ground. Since length of coil "C" is twice length of coil "H" winding, magnetic field generated by coil "C" is twice as strong as magnetic field by coil "H". Therefore needle will be pulled to "C" position. When ECT temperature increases, resistance in ECT sending unit decreases. Since voltage flows to path of least resistance, more voltage will begin to by-pass "C" coil and travel directly to ground through ECT sending unit. Under these conditions coil "H" magnetic field becomes stronger than coil "C" magnetic field and needle moves toward "H" position.