In general, yes, covering your outdoor Air Conditioning condenser unit in the winter is a good idea. It will help prevent dirt, leaves, and other debris from getting in the condenser fan and the coils. It might help extend the life of the condenser unit or just make it easier to clean in the spring. You can cover the unit with a tarp or plastic sheeting and some weatherproof twine. Make sure the covering is NOT air tight so moisture can evaporate if trapped inside the unit. Trapped moisture could promote rusting of the equipment. Also be sure to remove the cover before turning the unit on. Be sure the unit is not a heat pump which needs to be UNCOVERED in the winter.