Mercury F2AZ-12A648-A Sender Assembly

The coolant temperature indicator system includes a dashboard gauge and a sending unit on the engine. The unit's location varies depending on the engine model. Some vehicles have multiple units, but only one is used for the indicator system. On 2005 and later Expedition/Navigator 5.4L engines, a cylinder head temperature sensor is used. If overheating is indicated, check the coolant level, wiring, and fuses. To test the sender, disconnect the connector and attach a jumper wire. If the gauge doesn't swing to full hot, there may be a circuit issue. If the gauge works during testing but not when hot, replace the unit. Prepare the new unit with Teflon tape or sealer. For 2005 and later models, the intake manifold must be removed to access the CHT. Disconnect the connector and unscrew the sensor to replace it. Install quickly to minimize coolant loss and check the coolant level after installation.