The first step in cleaning your AC coils is obviously getting access to them. The evaporator coils are found inside your indoor handling unit behind the removable access panel. Before doing anything, make sure you turn the air conditioner off at the thermostat. You may want to shut off your circuit breaker just to be safe! Then, remove the screws or fasteners and loosen the panel, making sure to place the panel and screws aside where they wont get lost.
Next, use one of the following techniques to clean your AC evaporator coils:
1. Using compressed air. If there isn't a large buildup of dirt on your coils, it can usually simply be removed with the use of compressed air to blow the dirt off the evaporator coil. You'll want to direct the compressed air in the opposite direction of the normal air flow across the coil. Also, make sure that you use a consistent airflow across the coil, wear eye protection and use a shop vac to clean up the dirt and debris as it become dislodged.
2. Using a brush. This can be an effective technique for removing light amounts of dirt from the coils, also providing you more control on the pressure and areas that are being cleaned. With this method you'll use the brush directly on the coils to sweep the dirt away, scrubbing if necessary for harder to remove dirt. You'll want to use a soft brush, avoiding hard bristles or wire brushes as they can cause damage to the fins.
3. Using commercial cleaners. You'll have choices when it comes to the selection of cleaners available for cleaning your evaporator coils. After selecting your preferred brand, follow the instructions that come with the cleaner. Let the cleaner sit and foam until both the foam and debris drain away. Reapply as necessary (or per the instructions) until the coils are free of buildup and are clean.
4. Using mild detergents and water. If you prefer not to use a commercial cleaner, a mild detergent and water works just as well sometimes to clean the coils. Mix a simple detergent and warm water in a spray bottle or garden sprayer. Spray the solution onto the evaporator coils and give it a few minutes to soak in and loosen the dirt and debris. Wipe away any loosened material with a soft brush or cloth and reapply as needed.
5. Heavy-duty cleaning. If your evaporator coils are heavily soiled, you may need to use heavy duty cleaning chemicals and equipment like a steam cleaner or pressure washer. It may also mean you need to take apart more of your AC unit than just a regular cleaning, such as the removal of the coil, cutting of the refrigerant lines, and then reassembly afterwards. If this is the case for you, you'll want to consult with a professional HVAC contractor who can assess the job and will have the correct equipment, training and supplies to clean the coils and restore your AC system back to normal without incurring the risks of damage.