Temperature Gauge/Warning Light: Tracer

1. If temperature gauge always reads "COLD", ground Yellow/White wire at instrument cluster connector. If temperature gauge reads "COLD", replace gauge. If gauge does not read "COLD", proceed to step 2).
2. Ground Yellow/White wire at coolant temperature sending unit. If gauge reads "COLD", replace Yellow/White wire between gauge and sending unit. If gauge does not read "COLD", replace sending unit.
3. If temperature gauge always reads "HOT", disconnect Yellow/White wire from sending unit. If gauge does not read "HOT", replace sending unit. If gauge does read "HOT", proceed to step 4).
4. Reconnect Yellow/White wire to sending unit. Disconnect instrument meter connector. If gauge does not read "HOT", replace Yellow/White wire between sending unit and gauge. If gauge does read "HOT", replace gauge.
5. If temperature gauge is not accurate, disconnect coolant temperature sending unit connector. Connect leads of Rotunda Gauge Tester (021-00038) to the White wire of sending unit connector and the other lead to ground.
6. Turn ignition on, check that temperature gauge needle indicator displays correct resistance values. See Fig 1 .
7. Inspection should continue for 2 minutes. If gauge readings are incorrect, replace gauge. If gauge readings are correct, replace coolant sending unit.

Fig 1: Tracer Temperature Gauge Resistance Values

Courtesy of FORD MOTOR CO.