I know there is an old thread about this topic but I didn't have any luck with info that was on that one...My stock temp gauge stays close to zero, flickers up a touch occasionally.. Replaced the sensor and symptom didn't change. Grounding the wire swings the gauge needle all the way to max, so gauge seems okay by that check. I bought the car a year ago and it has been this way since I've owned it. Any help would be much appreciated

The stock installation could have had multiple temperature sensors. Which one was replaced - What wire color(s)?

I had replaced the lower sensor, down around the first two spark plugs on drivers side. That sensor connects to a single green wire, if I remember correctly without looking at it right now. (The sensor/plug up near the thermostat housing doesn't have anything connected to it. The fan still kicks in when warm, so I'm not sure what's tells that to turn on.)

Bad ground? look to see if the braided wire from the engine block to the firewall by the HVAC box (at least that is where mine is located) is still in place.
I had a similar problem with an S10 Blazer years ago. The previous owner had a valve job done, and the gauges were flakey. Found that the ground was not connected; solved all my problems..

I am hopeful/willing to try anything new. Wouldn't a bad ground affect other gauges then? Everything else seems to work fine..