How to Clean AC Coils Inside a Furnace Without Removing Them

How to Clean AC Coils Inside Furnace

Maintaining a furnace is a critical aspect of home care, particularly when it comes to its internal components, like the air conditioning (AC) coils. These coils play a pivotal role in the efficient operation of your heating and cooling system. Over time, dust, dirt, and debris can accumulate on the coils, significantly impacting the performance and efficiency of your furnace. Cleaning these evaporator and condenser coils is essential, but the task can seem daunting, especially if you’re considering removing them for a thorough clean. However, it’s possible to effectively clean your AC coils inside the furnace without going through the hassle of removing them. This not only saves time and effort but also reduces the risk of damaging these delicate components. In this article, we’ll guide you through a simple yet effective process to clean your AC coils inside the furnace, ensuring your heating and AC system operates at its best without the need for complex disassembly.

Understanding Your Furnace and AC Coils

Before delving into the cleaning process, it’s important to understand what AC evaporator coils are and their significance in your furnace system. Air conditioner coils, specifically the evaporator coils, are found in the air handling unit of your furnace. They are crucial for heat exchange – the process that cools and dehumidifies your indoor air. When your furnace runs in cooling mode, the evaporator coils contain refrigerant that absorbs heat from the compressed air passing over them. This not only cools the air but also removes excess moisture, contributing to a comfortable indoor environment.

However, the efficiency of this process can be severely hampered by dirt and debris build-up on the coils. Dirty coils can restrict airflow and insulate the coil, reducing its ability to absorb heat and causing the system to work harder. This leads to increased energy consumption, higher utility bills, and the potential for system malfunctions or breakdowns. In extreme cases, it can even lead to the freezing of the coils, further impairing the system’s functionality.

Regular cleaning of the AC coils is, therefore, not just a matter of cleanliness but a crucial maintenance step for the health of your furnace. By keeping the coils clean, you ensure that your furnace operates efficiently, maintains indoor air quality, and prolongs the lifespan of the system. In the following sections, we’ll guide you through the steps to safely and effectively clean these coils without the need to remove them, ensuring your furnace remains in top condition.

Preparation for Cleaning

Before you start the cleaning process, it’s crucial to prepare adequately to ensure safety and effectiveness. Here’s what you need to do:

  1. Safety First: Turn off the power to your furnace. This is an essential safety step to prevent any electrical accidents. The power switch is usually located near the furnace or on your home’s main electrical panel.
  2. Gather Your Tools: You will need a few basic tools for this task. These include:
    1. A soft brush or an evaporator coil brush
    2. A vacuum cleaner with a soft brush attachment
    3. A spray bottle filled with a mild detergent solution or a specialized coil cleaner
    4. Clean, lint-free cloths
    5. Protective gloves and eyewear
  3. Access the Coils: Depending on your furnace model, you may need to remove a panel or access door to reach the coils. Typically, this involves unscrewing or unfastening some screws or fasteners. Be careful not to damage any wiring or components while doing this.
  4. Inspect the Coils: Before cleaning, inspect the coils for any visible damage like bends or cracks. If you notice significant damage, it’s advisable to contact a professional for repair or replacement.
  5. Prepare the Area: Place a small tarp or old towels around the work area to catch any drips and protect the surrounding space from the cleaning solution.

With these steps completed, you’re now ready to start the actual cleaning process, which we’ll cover in the next section.

The Cleaning Process

Cleaning the AC coils inside your furnace is a delicate task, but with the right approach, it can be done efficiently and safely. Follow these steps to ensure a thorough clean:

  1. Brush Off Loose Debris: Using a soft brush or a specialized furnace coil brush, gently brush away any loose dirt or debris from the coils. Be gentle to avoid bending the fins or damaging the coils.
  2. Vacuum the Coils: Attach a soft brush to your vacuum cleaner and carefully vacuum the coils. This will remove the dust and debris loosened by the brushing. Ensure the vacuum is set to a low suction level to avoid damaging the coils.
  3. Apply Cleaning Solution: Fill your spray bottle with a mild detergent solution or a commercial coil cleaner. Spray the solution onto the coils, making sure to cover them evenly. Let the solution sit for a few minutes to break down the dirt and grime.
  4. Gently Wipe the Coils: After allowing the cleaning solution to settle, use a clean, lint-free cloth to wipe the coils gently. This will help remove any remaining dirt and cleaning solution. Be careful not to press too hard and damage the coils.
  5. Rinse if Necessary: If your cleaning solution requires rinsing, gently spray water over the coils and then wipe them down again with a clean cloth. Be cautious not to wet any electrical components.
  6. Dry the Coils: Allow the coils to air dry completely. You can also use a soft, dry cloth to gently pat them dry.
  7. Reassemble and Test: Once the coils are dry, reassemble any panels or doors you removed. Turn the power back on to your furnace and test the system to ensure it’s working properly.

Regular cleaning of your AC coils will not only improve the efficiency of your furnace but also extend its lifespan. This routine maintenance can save you from costly repairs and ensure a comfortable home environment.

Post-Cleaning Care and Maintenance Tips

After successfully cleaning the AC coils inside your furnace, it’s important to focus on their ongoing care and maintenance. These tips will help you keep the coils in top condition and ensure the longevity of your furnace:

  1. Regular Inspections: Make it a routine to inspect the coils periodically for dirt buildup, especially during peak usage seasons. A quick visual inspection every few months can help you determine when they need cleaning.
  2. Change Air Filters Regularly: One of the simplest yet most effective ways to keep your coils clean is by regularly changing the air filter in your furnace. Dirty filters can lead to dust and debris accumulation on the coils. It’s recommended to change the filters every 1-3 months, depending on usage and the type of filter.
  3. Ensure Proper Airflow: Ensure that vents and registers in your home are not blocked by furniture or other objects. Proper airflow helps in maintaining the efficiency of the furnace and reduces strain on the coils.
  4. Annual Professional Maintenance: While DIY maintenance is crucial, having your furnace and components like the air handler inspected and serviced by a professional annually is equally important. This ensures that any potential issues are addressed before they become major problems.
  5. Be Alert to Signs of Problems: Pay attention to any signs that your furnace is not functioning properly, such as strange noises, reduced heating or cooling efficiency, or unusual smells. These could indicate an issue with the coils or other parts of the furnace.

By following these post-cleaning care and maintenance tips, you can ensure that your furnace remains efficient and effective for years to come.

⚠️ Common Mistakes to Avoid


When cleaning AC coils inside a furnace, it’s easy to make mistakes that can lead to bigger issues. Being aware of these common pitfalls can save you time and money in the long run:

  1. ⚠️ Skipping Power Off: Never start cleaning without first turning off the power to your furnace. This is a critical safety step to avoid electrical shocks.
  2. Using Harsh Chemicals: Avoid using harsh or abrasive cleaners on the coils. These can cause corrosion or damage to the delicate fins. Always opt for mild detergents or specialized coil cleaners.
  3. Applying Excessive Force: Be gentle when brushing or wiping the coils. Applying too much force can bend the fins, reducing the coil’s effectiveness in heat exchange.
  4. Ignoring Leaks: If you notice any moisture or leaks around the coils, do not proceed with cleaning. This could be a sign of a refrigerant leak, which requires professional attention.
  5. Forgetting to Replace Panels: Always remember to replace any access panels or doors you removed during cleaning. Operating the furnace without these can be unsafe and affect its efficiency.
  6. Neglecting Regular Maintenance: While cleaning the coils is important, it’s just one part of overall furnace maintenance. Don’t overlook other aspects like filter replacement, duct cleaning, and annual professional inspections.
  7. Attempting Repairs Beyond Your Skill Level: If you encounter issues that seem complex, like an issue with the indoor air handling unit, it’s better to consult a professional rather than attempt DIY repairs that could exacerbate the problem.

By avoiding these common mistakes, you can ensure that your evaporator coil cleaning process is safe, effective, and beneficial for your furnace’s long-term performance.


Cleaning the AC coils inside your furnace is a critical maintenance task that should not be overlooked. By following the steps outlined in this guide, you can effectively clean your coils without the need to remove them, ensuring your furnace operates efficiently and reliably. Regular cleaning not only enhances the performance of your heating and air conditioning system but also extends its lifespan and helps maintain a comfortable and healthy living environment.

Remember, while DIY maintenance, like coil cleaning, is important, it’s also crucial to complement these efforts with regular professional check-ups. This ensures that all components of your HVAC system are in optimal condition and any potential issues are addressed timely.

By staying vigilant about furnace maintenance and avoiding common cleaning mistakes, you can enjoy a well-functioning HVAC system that keeps your home comfortable throughout the year. With a little effort and care, your furnace can continue to provide reliable heating and cooling, keeping your home cozy and your energy bills in check.

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