Engine Cooling problem
2006 Mazda 3 4 cyl Four Wheel Drive Automatic 90,000 miles

Hi,
Wondering if anyone can help.My Mazda 3 temp gauge is sitting higher then normal around half but I have owned the car since new and has always sat at a 1/4.When I travel down hills the temp gauge drops by 4 lines the jumps back up.The cooling fan only works with the AC on,it is not going through fluid.I have replaced the cooling system sensor and that did nothing.When the car was hooked up to there machine and was reading that the engine and cooliant are too hot but the gauge stays the same.