why is my temperature gauge moving? on 2004 Dodge Ram 1500

temperature gauge was moving past half way and the go back to normal,so i changed the thermostat and fluids, and the gauge continues to move back and forth, just now way the thermostat opens and closes that much, but the needle still moves past half way and then eases back to half and then back past halfway...

Asked by for the 2004 Dodge Ram 1500
Need to Diagnose this issue, which takes a skilled tech, a scanner and some real experience. here are some shops
2 more answers
Had same problem. Started trouble shooting as you did replaced thermostat and housing gaskets, radiator cap and flushed radiator. However upon further investigation it was the radiator itself. Apparently the orange type coolant that the dodge takes tends to gunk up easily and should be replaced every 30000 miles if not then you guessed it replace the radiator. Im sure this is the problem radiators are about 160-185 dollars and very easy to replace yourself.
Hi you due. Do you already fixed you problem.because i have the same