How to Clean the Evaporator Coils on a Central AC Unit

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Removing Stains

There are five essential tools required to clean the evaporator coils on your AC unit, including a stiff brush, a screwdriver, household bleach, a large hand mirror, and wire. Before proceeding, locate the evaporator coils. For a central air system, the evaporator is typically positioned directly above the furnace in the plenum (main duct). In case the plenum is sealed shut, do not attempt to open it, as it indicates that you do not have an AC unit that can be cleaned independently.

If you can open the plenum of your AC unit, the first step is to remove the foil-wrapped insulation at the front of the plenum. This insulation is typically taped in place; thus, carefully remove the tape. You can put it back later. After removing the insulation, an access plate will be visible. Use a screwdriver to remove the screws holding the plate in place and take out the access plate.

The evaporator itself should now be visible. Even if they have rigid pipes, some evaporators can be partially removed, but be cautious when doing so. Use a stiff brush and a large hand mirror to clean the underside of the evaporator unit.

Additionally, clean the tray beneath the evaporator. The tray’s purpose is to carry away condensation from the evaporator. Pour one tablespoon of bleach into the weep hole to prevent fungus growth. If the tray has a lot of moisture, the drain line connecting the weep hole to the tray might be blocked. In such cases, you can unblock the drain line by pushing a wire through it.

After cleaning, push the evaporator back to its original position (if you’ve moved it) and screw in the access plate. Finally, re-tape the insulation over the plenum.





1. Why is it important to clean the evaporator coils on a central AC unit?

It is important to clean the evaporator coils on a central AC unit because dirty coils can reduce the efficiency of the unit, resulting in higher energy bills and potentially causing damage to the system. Additionally, dirty coils can lead to poor indoor air quality and may even cause the unit to stop working altogether.

2. What are some signs that the evaporator coils need to be cleaned?

Signs that the evaporator coils need to be cleaned include reduced airflow from the vents, an increase in energy bills, and the unit taking longer than usual to cool the space. Additionally, if you notice a musty or moldy odor coming from the vents, this could be a sign that the coils are dirty and need to be cleaned.

3. Can you clean the evaporator coils yourself, or do you need to hire a professional?

You can clean the evaporator coils yourself, but it is important to proceed with caution to avoid damaging the system. It is recommended to hire a professional if you are not confident in your ability to safely and effectively clean the coils. Additionally, if your unit is still under warranty, attempting to clean the coils yourself could void the warranty.

4. What is the best way to clean the evaporator coils?

The best way to clean the evaporator coils is to use a soft brush or cloth to gently remove any dirt or debris that has accumulated on the coils. It is important to avoid using any harsh chemicals or abrasive materials, as these can damage the coils. If the coils are heavily soiled, it may be necessary to use a commercial coil cleaner, but this should only be done by a professional.

5. How often should the evaporator coils be cleaned?

The frequency with which the evaporator coils need to be cleaned will depend on a variety of factors, including the age of the unit, how often it is used, and the air quality in the home. As a general rule, it is recommended to have the coils cleaned at least once a year, but it may be necessary to clean them more frequently in certain circumstances.

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