Mercury F5AZ-12A648-AB Sender Assembly

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The dashboard gauge and the computer's fuel/air adjuster have different senders. The first one has a single wire while the latter has two or three. They are not placed in the same locations depending on the type of engine you have. For replacement, wait for the cooling system to cool off, open the pressure cap to release pressure, and then replace it. Disengage the electrical connector from the sender unit; uninstall it and promptly install another to minimize loss of coolant. Reattach electrical connection, inspect coolant level, and check if there is leakage when you start your car again.

The coolant temperature indicator system includes a dash warning light or gauge and a temperature sending unit on the engine. Four-cylinder and post-2008 V6 models use a Cylinder Head Temperature sensor, while pre-2009 V6 models use an Engine Coolant Temperature sensor. These sensors inform the Powertrain Control Module and function as the coolant temperature sending unit. If overheating is indicated, check the coolant level and wiring harness connectors. The indicator light should come on when the ignition is turned to START and go out once the engine starts, unless the engine overheats. If the light doesn't behave as expected, it could be due to a faulty bulb, ignition switch, circuit, grounded wire, or sending unit. Ensure the coolant is correctly mixed to activate the sending unit.

If an overheating indication occurs, the coolant level should be checked and all connectors in the wiring harness between the sending unit and the indicator light or gauge should be ensured to be tight.

Camshaft Position (CMP) sensor replacement involves disconnecting the battery, detaching the electrical connector, removing the sensor, and aligning the new one correctly.

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 2005 and later Expedition/Navigator 5.4L engines, the intake manifold must be removed to access the Cylinder Head Temperature (CHT) sensor. The pressure cap from the degas bottle should be removed to release any remaining pressure in the system before reinstalling it.

If the light doesn't go out, you should check the coolant to make sure it's correctly mixed. Plain water with no antifreeze, or coolant that's mainly water, might have too low a boiling point to activate the sending unit.