I have a 2006 chevy impala lt 3.5 here lately the display on the dash says engine hot a/c off then the temperature gauge drops all the way down to Cold. The car can sit all night and when I start it in the morning the message still pops up and the gauge is on cold. I can unplug the battery and hook it back up then it runs fine for about two days or I will be driving down the road and the message disappears and the gauge goes back up. The message also will pop up just while I'm driving down the road as well. I have replaced the thermostat and the coolant sensor not that long ago and it fixed the problem for about two week. The other day on my way home from work the message popped back up and gauge dropped all the way down to cold and no one can tell me what is wrong with it. Any one else have this problem or have any idea what this could be caused from?

The problem may be an internal fault with the Instrument Panel Cluster (IPC).
That opinion will require verification by a knowlegable tech with the proper scan tool to evaluate if the correct signals are getting to the IPC and the IPC is misunderstanding the signal.