I had this problem on a 2001 Ford Fiesta. I ended up having to get the temparature gauge sender unit replaced.
yes
i change the thermostat and the temp switch but still not working
Test gauge function with a mechanical gauge to get actual engine temp.
most likely the gauge
Thermostat is gone, change it
that is not a question
Change your thermostat.
Not sure what you really mean but if temp of heat does not change = likely bad thermostat etc. If gauge does not work at all but heat is fine then gauge or electrical type problem to the gauge
The temperature gauge on a car fluctuates because the car's thermostat is opening and closing. The gauge goes up when the thermostat closes and the gauge goes down when the thermostat opens.
thermostat may be sticking and that cause the gauge to show hot, have it checked soon, you could be headed for bigger problems
check the connections behind the gauge they could pop loose
You most definately unpluged the sensor wire. It's a single red wired that plugs onto a sensor just passed the thermostat.