Coolant Temp Guage

I hate this thing. The car is a 1993 Chevrolet Lumina Euro sedan. V6 3.1 My temp gauge fluctuates from normal temp to hot all the time or it just says its hot all the time even when I just turn on the car. I changed the temp sensor in the engine twice. Then I looked at the pigtail. The wires were burned so I got a new pigtail and soldered it in. It read the right temp for a couple minuates then it shot to overheating again. I'm completely lost at this point. What else could be doing this? Also my primary fan won't turn on but my a/c fan does. I tested the primary fan motor and it works. But it won't turn on when it needs to.

I'm asking about a 1993 chevy lumina when I typed in all my info on the page when I hit enter it used the info from one of my other cars. Yes I check all the basics.

I have a BMW And it over heats what do I do.