Driving my 2016 Expedition two weeks ago I noticed a bunch of condensation on the rings around the vents. Didn't think too much about it, but the next day after driving it again, I hear a pretty loud hissing sound at the rear of the vehicle after it was turned off. The day after that, AC stops working altogether, and only blows hot air.
Had my local Ford deal put some dye in it, and they found the leak where the lines connect to the rear auxiliary evaporator. Quoted $3,200 to replace the 2 tubes/fittings associated with the AC. They also told me there are four lines/hoses down there in total (the other two for the heat), and said advised they all replaced together, along with the evaporator itself. The quote for this was a little over $5,200.
I certainly don't have the expertise/equipment/time to handle a job like this on my own, but this cost is a tough pill to swallow.