Engine Coolant Temperature Gage

The Engine Coolant Temperature Gage is operated by two coils. Battery voltage is applied to both coils. One is grounded directly and the other is grounded through the Engine Coolant Temperature (ECT) Sensor. This has 63 ohms resistance at 125°C (260°F) (hot coolant) and its resistance increases at lower temperature. Resistance is approximately 1365 ohms at 40°C (100°F). This causes the current through the sender and one coil to increase as the engine coolant temperature increases. This moves the pointer.