yes
Test gauge function with a mechanical gauge to get actual engine temp.
that is not a question
thermostat may be sticking and that cause the gauge to show hot, have it checked soon, you could be headed for bigger problems
Could be low on coolant (leak somewhere) or the thermostat is faulty.
i change the thermostat and the temp switch but still not working
With the thermostat.
A faulty thermostat might cause the temp gauge on the 2000 Nissan Altima to raise to hot when the car is not overheating. A faulty thermostat can cause the gauge to move up and down and might even turn the fan on.
Stuck closed thermostat. Replace the thermostat.
a bad, or no thermostat might be suspected.
I had this problem on a 2001 Ford Fiesta. I ended up having to get the temparature gauge sender unit replaced.
Thermostat stuck open or no stat at all. Faulty temp sensor or Gauge.
because your thermostat is opening and closing as the engine temp. fluctuates