I run a 165 degree thermostat in my engine and have the fan programmed to come on at 180. It must be programmed to come on at a higher temp than the thermostat or it will run all the time. One other thing to consider is the location of your temp sensor and your fan sensor. My fan sensor is located in the bottom of the radiator which causes it to come on at 180 when the car is just sitting around idling but.....If the car is on the interstate the fan will not come on until the temp gauge is sitting on 200 degrees. The fan sensor is reading the coolant temp coming out of the radiator while the temp gauge is reading the coolant temp going into the radiator or leaving the engine. The point is you need to be aware of the big picture when you install your fan sensor. If you can install it in the head or intake manifold it would probably be best. I am used to how mine operates and don't give it much thought.