colant temp guage dont work... where do i start? the sensor?

 

Eh, there is a troubleshooting process that includes grounding the sensor wire to see what the gauge reading is. Can't remember the entire procedure - but a shop manual such as Haynes, Chiltons, or Ford should spell it out.

My coolant temp gauge sensor has failed twice since I've owned the truck.

Good luck, and keep us posted.