its been like this for awhile stays under the 140 mark so i know its not reading anything. do you guys know how to check if its the gauge tach itself or the sensor?

 

unplug sensor from front of motor. then turn the key on. if the gauge and wiring are good the gauge should read max like 240

 

I have been having a different but somewhat related problem. My 95 Ram 2500 Cummins 12v. While driving the temp gauge will go up and down never into the red but prob as high as 190-210 then drops to below average operating temp then climbs again no steady temp any ideas?

 

Coolant temperature flucuation is normal in 12v's, thats just how the thermostat works. Completely normal