The plastic material that forms the AC cover / shroud tends to harden over time. They generally last 5 years, at which point they should probably be replaced, but who really tracks that.
We’ve all seen these AC shrouds on the side of the road after being blown off an RV. Although I inspect them at the start of each RV season, we had the “blow off” occur to us.
I always thought you would hear something when this occurred, but no such luck. What we did notice was when it began raining later that night, water was dripping into the coach from the front AC. A quick roof inspection and a “there’s yer problem” moment later, we created a makeshift shroud from plastic trash bags and good old duct tape.
What seems to happen is the front area of the cover, where the screws go through, crack over time. Once you are going down the road, air can get under that front lip and if there is enough weakness at those screw locations, the shroud will lift and separate and be free to roam the interstate system.
That front lip also flexes a good bit when you reinstall the cover after cleaning the coils and getting the mud dauber nests removed. That flexing does nothing for its life.
When we recently replaced our AC units (due to a failure), I decided to reinforce the front screw openings on the new shrouds during my next round of annual roof maintenance.
I fiberglassed in thick pipe hanger material behind the existing openings. My intention is to spread the screw clamp load and fill the gap that allowed the cover edge to flex when the screws are tightened. The area is much stiffer now, and the front gap between the shroud and the A/C body is now pretty much closed.