I know the circuit is good because the needle starts at C and slowly creeps up to H.
Other than that. I don't know much. In the winter, it stays at operating temp. 1/3 climb of needle. In the summer it goes to H. I use a heat sensor gun and it registers about 165 degrees without a thermostat and 185 with a 180 degree thermostat. But the temp gauge reflects engine is overheating. :(