I have been noticing a lot of A/C covers cracked around the lower edges and at the mounting holes where the screws are attached. It is important to make sure that the covers are securely attached, but it appears that many owners (or repair shop personnel) are tightening the screws too much so that they cause the cover to crack. Use caution and less muscle when attaching the cover.
It is also important to inspect the covers from time to time to make sure that any cracks in the cover are not growing. I have had success repairing the plastic covers with fiberglass cloth and fiberglass. The repair kits can be found in most automotive parts departments. The repair doesn’t take long and the fiberglass hardens very quickly. I make all repairs on the inside of the cover so the repair is not seen when the cover is installed.
Instructions for preparing the surface to be repaired and applying the glass and resin are provided with most repair kits.
If the cover is already cracked around the hole, you might save the cover by adding a large surface washer under the screw to spread the force of the screw on the cover. This will work if the crack has not spread too far.
If the cover is damaged and not repaired, the wind force may further damage the cover due to vibration and eventually allow the cover to be blown from the roof of the RV. Replacement cost may be around $100.