Okay, as I've previously mentioned, my 1994 F150 had engine issues, and I've replaced the engine with a rebuilt unit. In the process of swapping over the sensors, I noticed that there are TWO coolant temp sensors: one by the thermostat, that sends a signal to the dash gauge, and one on the rear of the block, that sends data to the ECU.
This seems odd; that Ford would (seemingly) needlessly spend excess cash installing two sensors, when one would do, sending data to two places. Leading me to believe it isn't really needless: there must be some advantage to such a setup, or they wouldn't do it. Further augmenting this belief is the fact that another car I've owned (1998 Contour) had just such a setup.
So...why is it like this? What is the advantage?