ok when my temp gauge stops working so does my a/c and heat and it says engine hot a/c turned off eve if the truck has been sitting all night in 30 degree weather all fluids are good truck is not actually running hot and as soon as my temp gauge starts working everything else starts working again and it stops saying engine hot A/Cturned off any suggestions?

I would start by replacing the temperature sending unit. If this is bad, it affects everything on the engine. Not sending the computer the right information it needs to adjust other sensors.

I have replaced thermostat AND sending unit twice. Problem did not go away.

I’m having the same problem Just replaced coolant temperature sensor going to replace thermostat