Mine is the same way. Getting louder as its gets colder. I took it to the dealer and the dealer told me the sound is normal. Funny thing is I cant hear the fan when I'm in my buddy's ram. I'll just keep bringing it in till they get sick of seeing me..

 

Going to dealer tomorrow morining they ordered the fan so we will see what happens I have been less then pleased with both dealers in my area almost regretting I went with this truck I have been back with this truck in 6 months almost as many times as I have been back in 3 years with my Magnum and the service reps make it seems like they are doing you a favor by addressing issues getting very frustrating!