Is it safe to cover and outdoor central air conditioning unit in the winter, and will it help the furnace produce more heat if you do?
You can insulate the pipe or hose running from the unit to the house, but covering the entire unit...I don't know for sure, but I think that could be bad.
You can cover the outdoor unit of a central air conditioner to shield it from winter weather and debris. It also keeps the rainwater, snowfall, ice, and other precipitation from sipping through the top and side vents.
You can cover it to keep any moisture from getting inside although it won't hurt it. It does nothing to help the heating of your house.