Had this issue with my 2015 Super-Crew 5.0 liter F150.I first observed the temperature indicator appeared to be in its normal temperature range during summer driving in New Mexico. I shutoff my A/C while the engine was still running, and within 45 seconds the obnoxiously loud, high flow fan shutoff. I shut the engine off for 30 minutes (resetting the computers and sensors). I started the vehicle and let run for 30 minutes, in that time not once did the high flow fan turn on. By segregating the A/C from the rest of the cooling system, I was able to see if the high flow fan was turning on due to the A/C or something else in the cooling system.
I have the equipment and experience to evacuate the refrigerant, contaminants, check for leaks and recharge the A/C. Many people do not and I strongly recommend you have an A/C certified professional do this work. This ensure the A/C system is properly, cleaned out, leak checked and recharged. Pressure verification and contaminant removal prevents an over pressure (or fluctuating pressure) situation as the contaminants can see the 3 states of matter due to the low and high temperatures created during the refrigerant compression cycle. Lastly, most contaminants are injected into the system due to the person recharging not properly cleaning the recharge fitting (Schrader Valve) free of contamination before recharging)
There are essentially 3 cooling interlocks in the F-150 system, and they are interpreted by the trucks software in the following priority
- A/C High pressure sensor/switch (this is # 1 due to the system containing a gas/liquid vapor refrigerant that is compressed to create heat exchange. Pressure increases with increasing temperature, as well as contaminants in the system can create explosive pressures in this system
- Left and Right cylinder head (engine) temperature switches
- Coolant water temperature sensor