Cause of temp gauge flatline after change
 

Noticed a lot of people had dash temperature gauges fail after installing new sensor,Why?

Because the aftermarket sensors given will not work on a 1 wire 3.0 system,they will not ground it. Autozone for example gives you a SU284,it has no continuity fron the blades to the base,so it will not ground the 1 wire harness,as other aftermarkets also do.

Solution to fix gauge,
get a motorcraft SW-5174, F7DZ-10884-AA,it ground the blades and is the correct sensor for a 1 wire temp gauge.