Originally Posted by Hurricane34J
So would I just replace the alternator?
Food for thought
Before you start spending a lot of money and engage in changing and praying (change a part and pray it fixes the issue) I recommend taking the coach to a Ford truck center and have them do a diagnosis. The hour of labor for the diagnosis may be saved in parts restocking fees you have to pay when you return items that didn't fix the problem. Some electronic parts can not be returned unless they were defective at purchase. For example, folks mentioned bearings. There are bearing on idler pulleys, bearing on alternator, bearing on water pump, bearing on fans. How many parts must be changed before you find the culprit.
Then again, like I always say, you are free to do whatever your wallet can afford. Taking it to a Ford service center might get the issue fixed under warranty.
Again, just food for thought.