94 stock temp gauge jumps

[finalgray]

I got a 94 4.0 ranger 5-speed, and the stock water temp gauge will jump bad, like say its at half way running temp, ill turn the heater on or anything and the temp will automatic jump to three quarters. And it never stays in one spot, when it moves, as i said before it jumps from about half way to three quarters. Iam pretty sure my truck cant get super hot then normal temp and below that quick, so do i need to replace temp gauge? ohh, and its got a brand new thermostat on it sooo

[toddler62]

Its sounds like something is not getting a proper ground.Maybe a loose wire at sending unit or under dash