Should You Cover the Outside Back of a Wall Air Conditioner?

Why Cover the Back

• The back end of both window and wall air conditioner units extend out of the room, sitting on the outside. During colder, winter months, you don't use the air conditioner, but the back of it remains exposed to the changing elements, such as rain, snow, ice and winds. A unit left uncovered also allows in a draft. With a window air conditioner, you can remove the unit from the window, shut the window and store the air conditioner elsewhere for the winter. A wall air conditioner doesn't offer that luxury. If you remove a wall air conditioner, you're left with a gaping hole in the walls.

Why It Hangs Outside

• When you install a wall air conditioner, you must install it so that the back of it extends through an exterior wall, and doesn't rest on the inside. If you notice, the rear of the unit sits slightly lower than the front, so that the air conditioner can drain water to the outside, instead of onto the floor inside. This water is condensation, resulting from the moisture the unit removes from the room air. In addition to cooling the air, wall air conditioners dehumidify it, to improve your level of comfort.

Before You Cover It

• Before you cover the back of the wall air conditioner for the cooler months, seize the opportunity to conduct a little further preventive maintenance on the unit, so that it will be ready to perform when you need it again. Poke a wire up through the unit's drain hole, to make sure it is not clogged or obstructed. Start at the top on the back of the unit, and pull a fin comb down through any bent fins, to straighten them out. Be gentle and don't damage them. Make sure you obtain a cover that is sized to take into account both the unit and the support brackets underneath it, connected to the exterior wall.

Additional Maintenance

• In addition to preparing and covering the back of the unit, also perform other tasks before you store it for the winter months. Remove the unit's front grill and examine the filter behind it, or pull the filter out of its slot in the front grill. Replace the dirty filter with a clean one now. Also, vacuum out any dust and debris that might block the coils inside the unit, and use the fin comb to straighten out any bent fins.

How to Cover the Unit

• Obtain a cover designed for a window or through-the-wall air conditioner, from a local hardware or home improvement store. Know the model, brand and BTU size of your unit. These covers normally work on units that have or don't have support brackets, and are made from either vinyl or polyester. This is important, because these materials allow moisture inside the unit to escape, preventing rust. Wrapping plastic around the back of the air conditioner, then securing it with something such as a cord or tape, does the opposite and provides no way for that moisture to escape. Follow the specific cover manufacturer's instructions to install the cover. Installation usually involves sliding the cover up over the back of the air conditioner, and securing it with an elastic strap.