Mercury E1AZ-12A648-A Coolant Temperature Sensor

The coolant temperature indicator system has a dashboard light and engine-mounted sending unit. If overheating is indicated, check the coolant level, wiring, and fuses. The indicator light should glow when the ignition is on and the starter motor is running. If it doesn't, the bulb may be burned out, the ignition switch faulty, or the circuit open. Grounding the wire to the sending unit can help diagnose the problem. If the light doesn't go out after the engine starts, it could be due to a grounded wire, defective sending unit, or faulty ignition switch. Check the coolant type and mixture. If replacing the sending unit, disconnect the connector, unscrew the sensor, and use sealant on the threads. Ensure the engine is cool before removal and be ready for coolant loss. Check the coolant level after replacement.