Have a 2011 F-150 with a 5.0. Owned it for over a year and last night the radiator fans came on and were extremely loud. I've never heard them before.

I had driven 8 miles and it was 43 degrees outside, so my AC was not on. Drove to work this morning and the fans came on again after about 8 miles, and it's 34 degrees outside! Any ideas?

 

Sounds like the fan controller is defective. There should be a trouble code that would indicate where to look for the problem.

 

Have you checked the coolant? Temperature when they come on. Could also be a stuck thermostat.

 

Are you using the defrost mode when you warm your truck?

As far as I remember, defrost mode cycles the ac compressor which will cycle the fans.