I don't mean to pee on the parade but those covers crack because they are old and starting to crystallize from the weather.
The previous owner of my coach had done a repair like that on both of my covers and I got caught in a heavy wind storm and it blew off and destroyed the tubing and fins on the unit and lost all the coolant. If he would have replaced the cover I wouldn't be spending a $1000 to replace the unit. I bought 2 new covers and still need to replace the front a/c.
Dennis & Marcie & Hook The Jack Russell, 2001 HR Imperial 38wds 350 Cummins, 07 Chevy Trailblazer/Blue Ox/Ready Brake, 04 Dodge 3500 Cummins,