There is a reason to cover your air conditioner after the summer, and it’s not just for the winter snow. Your A/C unit is built to withstand the rain and snow, but it is not built to keep out leaves, seeds, or nuts. You will want to cover your system during the fall only when there is a chance of leaves or seeds getting into your air conditioner. If this happens leaves can create a place where moisture collects, which then causes corrosion.
When you cover your air conditioner, only cover the top of it. If you make your own cover, be aware that it should only come down the side about 6 inches. Don’t cover your unit completely. A cover that completely covers your unit will trap moisture inside which then causes rust and corrosion.
Covering your A/C unit in the fall prevents debris from getting in the top of it but covering the whole unit will trap moisture in.