electrical question

so i have been dealing with my overheating problem. and im down to testing the gauge. i read this in my fsm i found (The coolant temperature gauge gives an indication of engine coolant temperature. The coolant temperature sending unit is a thermistor that changes electrical resistance with changes in engine coolant
temperature. High sending unit resistance causes low coolant temperature readings. Low resistance causes high coolant temperature readings) and from what i read i should be at 1345ohms, but i am getting like 1910 ohms and my gauge still says im overheating. im thinking about wiring in a aux temp gauge to see if thats my problem. has anyone ever had problems with there gauge before?

OK need to knows here to help you out.....
year
engine size
open or closed coolant system

you say you are down to testing the gauge, what else have you checked? And where where you checking on the sensor to get your ohm readings? Did you isolate the sensor? Checking while not isolated will give you a false reading. It must be out of the head to test for ohms or you will get readings from the things connected to it as well. Was it still hooked up when you checked it? How warm was the sensor its self not the air temp it was out when you checked it. I am assuming you are looking at a chart with my last comment? All the charts are based off of sensor temp not the temp outside/inside when checking the sensor.