Welcome to the forum.
The fan comes on at mid point but when the engine is cold (when you first start up in the morning) and you turn on the AC, does the fan immediately come on? It should. If not, one of the speeds (2 speed fan) is burnt out. If it does, the only other suggestion is that you might have air in the system and it needs to be bled of any excess air. The bleed valve is located under the radiator cap.
