Ok so Ive been searching this everywhere and cant find an answer yet, when driving the car after a few minutes the temp gauge goes to half then to 3/4 or higher sometimes, just got this car too about two weeks ago. When I first got it the car would jump right to halfway when turned on. So far Ive flushed the coolant, replaced the temp sensor and the temp sending unit and the rad cap and made sure there wasnt any air in the system also did a compression test. So wtf is wrong unless its the gauge itself? Like last night the gauge dropped to below half when braking to go over a bump then when I let off the brake it moved and then more when I accelerated and down again when breaking. The fans arent working i gotta check the relay but that shouldnt matter when driving as the airflow thru the radiator would cool it down

 

I would swap the gauge out. I have had problems with stock gauges not being accurate. I have always considered stock gauges "screw me gauges" because by the time one lets you know there is a problem, your screwed!!! You can hit up the junkyards and should find that pretty easily.

 

To test the rad fan, unplug the ECT switch and with the ign. switch on jump the switch plug, if rad fan turns on it and all the wiring is good and either engine never got hot enough for rad fan to turn on or ECT switch is bad.

The ECT sensor has nothing to do with the temp gauge.

The ECT sending unit is what supplies the gauge with engine temp., if you unplug it gauge should not move, if it jumps around either the gauge is bad or there is a wiring problem, check the ground to the gauge, check continuity of the lead from the ECT sending unit and the gauge, should have full continuity, check for continuity to ground, there should be none. 94