my sons car again. Has 75k miles on it and this summer we replaced the head on it as overheated and warped the old one. At the time all was replaced including thermostat. He just came home from college and so dad checked things out
It appears the temp guage is not working as the needle stays in the cold range and only occasionally will fluctuate a bit just kinda bumping the needle a little then back to zero

So my question is..... Where is the water sensor element on the motor? Assumming that is what needs replaced. Any pics would help. I am handy with tools

 

There should be 2 sending units for coolant temp.
The first one is the coolant temp sensor for the computer's info. It has 2 wires, a Blk/White wire and a Lt Grn/Red or Lt Grn/Yellow wire.

The temp sending unit for the gauge has a single wire with a push on connector .
It should be located on the head. If you remove the wire the gauge should not register anything. If we grounded the wire the gauge should go all the way up to hot confirming wiring to be ok. Sometimes a poor connection with the push on plug will produce erratic readings. Sending unit not expensive and easy for you to replace if necessary.