WHEN the heat and humidity of summer take hold and it’s time to hit the “cool” button, you’ll want your air-conditioner to respond with a blast of chilly air and a satisfying hum.Doing some maintenance now can help make sure that happens.The first step, albeit a simple one, is often overlooked: Make sure the unit isn’t still wearing its winter coat, advised Richard H. Toder, executive director of T/S Associates, a Manhattan heating and air-conditioning company. “You wouldn’t believe how many people forget to take off the cover and end up burning their unit out,” he said., a home-improvement Web site.Look to see that weeds or bushes have not grown too close to the compressor, he said, and that no debris has been sucked up into the coil. The compressor should have at least a few feet of clearance around and above it, and its fins — a series of thin metal strips like those on the back of a window air-conditioner — must be free of dirt and debris.Next, remove the unit’s filter and either clean or replace it.

If the filter isn’t clean, the workings can become caked with dust, significantly reducing the unit’s efficiency. In window units, the filter is either a custom-fit plastic-framed fiberglass filter that can be washed and dried, or a plain foam one that Mr. Toder says should be replaced instead of cleaned. Buy a new one at a home center or hardware store for a few dollars and cut it to size.In central air systems, the filter is in the air handler, which is typically in the basement or attic. The filters — which often are also the furnace filters — come in specific sizes and can be found in hardware stores or home centers.“You don’t have to get a really expensive filter, as long as you resolve to change it every 30 days,” Mr. Carter said. A medium-price filter, costing about $5, is probably sufficient, he said. Most experts say it’s also important to clean the inside of the unit — particularly the evaporator coils, which look like a coil of copper tubing — with a vacuum cleaner or a soft brush.

With a window unit, that may involve removing the front cover to get to the coil; with a central air unit, you may need to take the cover off the housing of the evaporator coil. If that seems too complicated or difficult, call a professional.Peter Varsalona, a principal of Rand Engineering & Architecture in Manhattan, said that air-conditioners installed in sleeves through the wall — as in many apartments — can usually slide out of the sleeve and be cleaned.ac window unit how it worksOnce clean, the air-conditioner can be tested to make sure it still cools adequately. ac dc power supply schematicFor a window unit, the test couldn’t be more simple. through the wall ac units with heat“Wait until the temperature is about 70 degrees outside, turn the unit on, wait a couple of minutes, and if it’s blowing cold air, it’s working,” Mr. Carter said.

Tom Kraeutler, a co-host of the syndicated radio program “The Money Pit,” offers a relatively simple test for a central unit. Once the outdoor temperature reaches about 60 degrees, turn the unit on, let it run for 10 to 15 minutes, then put one room thermometer near a vent where the air is coming out, and another at one of the return vents, where air is pulled back to the unit.“What you are looking for is a 12- to 20-degree difference between them,” he said. If you don’t find that, he said, the unit could be leaking coolant and should be checked by a professional.John Proctor, president of Proctor Engineering Group in San Rafael, Calif., offered a few suggestions for using a central air system efficiently. Set the fan on auto, so that it comes on only when the unit is cooling the air, he said, and resist the urge to close exhaust registers in unused rooms. The system will operate more efficiently with all the registers open, he said.Cleaning suggestions for the indoor air handler of split system air conditioners, window air conditioners, and through-wall air conditioners & heat pumps.

This article describes simple cleaning procedures to remove mold from the air path of window or wall mounted indoor air conditioning or heat pump units. This article series describes split system air conditioning & heat pump systems. We review the major system components, switches & controls, and typical applications for split system cooling systems. We also discuss use of the remote thermostat control, where to find and how to clean the split system air filters, how condensate is disposed-of, and what to check first if your split system air conditioner is not working properly. These air conditioner mold removal steps will work on most window or through-wall air conditioners as well as on wall-mounted split system air conditioners and heat pumps. A split system or "ductless" air conditioning (or A/C & heat pump) system dispenses with duct work entirely, using a wall-mounted indoor evaporator/blower unit and a separate outside compressor/condenser (below left and right).

At above left you can see rather typical dark mold growth on the plastic surfaces of the indoor half of a wall-mounted split system air conditioner. Similar mold may appear on window or through-wall mounted air conditioners as well. Mold grows readily on the plastic surfaces of the air conditioner's face cover and on its air-directing louvers because these surfaces often are damp with condensate from the conditioned air. Mold may also grow on the metallic surfaces of the squirrel cage fan that blows room air through the air conditioner, more so as those surfaces accumulate building dust that typically includes organic debris such as skin cells. At left is a close-up of a fairly-clean split system air conditioner blower fan. If you click to enlarge the image you'll see normal dust accumulation on the blade edges. In contrast, if the curved blades have become dust-laden not only does that serve as possible mold food it also means that the air-flow of the blower fan will be reduced.

Don't panic if you see some black mold or dark brown mold in the blower portion of your wall-mounted split system air conditioner. Most commonly the fungus is a member of the Cladosporium sp. family (among those samples we've tested in our lab). Molds found in buildings may be relatively harmless, or allergenic, or sometimes more seriously harmful. Health risks are greater for people at extra risk themselves such as asthmatics, people suffering from allergies, the elderly, infants, and people with a compromised immune system. It is normal for dust and debris to collect on the fins of air conditioner air direction louvers, grilles, and squirrel cage blower fans. Typically this is harmless house dust and it's not a problem until it obstructs air flow. At left is a fairly dirty air conditioner air outlet grille or fan blade. But if the air conditioner is frequently wet, for example from condensate, that same dust can host the growth of a variety of molds, many of which are not highly dangerous.

However depending on the surface material that has been wet, sometimes different and more troublesome mold genera/species may grow. And if such areas in the building are large (more than 30 sq .ft. of contiguous mold) or if harmful molds are in the air path of building air handlers such as air conditioners, professional cleaning may be in order. See MOLD CLEANUP GUIDE- HOW TO GET RID OF MOLD if your building has a significant mold problem. All of these surfaces can be cleaned if you work carefully to avoid damaging cooling coil fins or knocking about the wall mounted unit and its components. You'll need some household spray cleaner (any cleaner will work but avoid using corrosive cleaners or agents on metal parts and avoid spraying your eyes). You'll also want some clean rags or paper towels and a clean soft bristle paint brush. Remove the plastic cover for the air conditioner and for best results, use your spray cleaner, paint brush, and a garden hose sprayer outdoors to clean the cover and its louvers.

You can do that job indoors too at a large kitchen sink. Now while the air conditioner's cover is drying there is more mold cleaning to do. Watch out: be sure that electrical power is off and disconnected from your air conditioner before removing its cover for cleaning or service. Otherwise you risk death by electrocution or cut or amputated fingers by moving parts should the equipment start while you're messing with it. While the covers are off of the indoor air handler unit of a split system air conditioner, if you take care not to bend or damage any components, the use of a simple household spray cleaner, paper towels, and a paint brush can clean out most of the mold that likes to grow on these frequently-damp surfaces in the air conditioner's room-air path. Using spray cleaner and dry paper towels we sprayed and wiped clean the easily-accessible areas of the wall-mounted air handler's surfaces taking care not to move, disturb, or break any louvers or other components.

You can see the black mold on our paper towel at above left. We also used a household-cleaner to wet our long soft bristle paint brush that in turn was used to gently clean the louvers of the blower fan (above right). Rinse the paint brush in clean running water, wet it again, and go back to continue cleaning the louvers of the squirrel cage blower fan until accumulated dust and debris have been removed. Watch out: take care not to spray or wet electrical components, and avoid spraying or wetting any fan bearings or you may be sorry you undertook this step. Watch out: if the cooling coil itself is badly soiled or blocked with dust and debris at your air conditioner or heat pump that tells us two things: At above-left is rather typical dark mold growth on the plastic components of a wall-mounted air conditioner. This mold growth is small in total area, is not deserving of panic, and would be of only trivial concern were it not in the air path of an air conditioner that circulates room air.