Mercury F5AZ-12A648-A Sensor - Engine Temperature, ECT

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Yes, some vehicles have more than one sending unit. One is used for the indicator system, while the other is used to send engine temperature information to the computer.

If the gauge reads full HOT when jumped but not when the connector is plugged in with a hot engine, the coolant temperature sending unit is faulty.

To replace the sensor, ensure the ignition key is in the OFF position and drain approximately one gallon from the cooling system. On 6.0L models, disconnect the wiring connector for the cooling fan, disconnect the electrical connector, and carefully unscrew the sensor. On 6.4L engines, remove the air cleaner housing to access the sensor, which is located near the base of the oil filter housing. Wrap the threads of the new sensor with Teflon sealing tape to prevent leakage and thread corrosion. On 6.4L engines, the sensor is sealed with an O-ring, so do not use tape, just install a new O-ring. Installation is the reverse of removal.

After replacing the ECT sensor, start the engine and allow it to reach normal operating temperature. Then, inspect for coolant leaks and check the coolant level in the expansion tank after the engine has warmed up and cooled down.

Drain coolant from the radiator to approximately four inches below the upper radiator hose.

To test the temperature sender, it should read in the cold range when the engine is cold. Disconnect the electrical connector from the sender and attach a jumper wire between the two pins of the connector. With the key ON, the gauge should swing to full hot. If it doesn't, there may be a problem in the circuit from the sender to the instrument panel.

Before replacing the sending unit, allow the cooling system to completely cool down and open the cooling system pressure cap to relieve any pressure in the cooling system. Install the cap to minimize coolant loss.

On V6 engines, the sending unit for the gauge is located on the front lower part of the intake manifold, near the thermostat housing.

For 2001 and later 2.3L models, disconnect the battery, expose the electrical connector, unscrew, and replace the Cylinder Head Temperature (CHT) sensor.

You should check for signal voltage (10 volts or more). Replacement involves disconnecting the electrical connector, removing the retaining bolt, and lifting the VSS from the transmission.

When replacing the sending unit, it is important to prepare the new unit by wrapping its threads with Teflon tape or applying sealer.

If an overheating indication occurs, it is important to check the coolant level and ensure the wiring and fuses are intact.

The coolant temperature indicator system consists of a light or temperature gauge mounted in the dash and a coolant temperature sending unit mounted on the engine.

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