How to Clean AC Evaporator Coil for Powerful Cooling

Air conditioners have 2 coils, one inside the house and the other one outside the house. The coil inside the house is called the evaporator coil while the one outside is called a condenser coil.

dirty evaporator coil
Underside of a dirty evaporator coil

Here is a summary of the steps to effectively clean the AC evaporator coil:

  • Safety First: Prior to beginning any maintenance, ensure the power to the AC unit is switched off at the circuit breaker to prevent electrical accidents.
  • Gather Necessary Tools: You will need basic tools such as a screwdriver, a soft brush or fin comb, a spray bottle, a no-rinse coil cleaner, and safety gear like gloves and safety goggles.
  • Access the Evaporator Coil: Depending on your AC unit’s design, you may need to remove an access panel or open a compartment to reach the evaporator coil. Refer to the manufacturer’s instructions or consult a professional if needed.
  • Inspect and Remove Debris: Carefully inspect the coil for dirt, dust, and debris buildup. Use a soft brush or fin comb to gently remove any loose particles from the coil’s fins.
  • Spray Coil Cleaner: Spray a no-rinse coil cleaner onto the evaporator coil as per the product’s instructions. This cleaner helps dissolve and remove stubborn dirt and grime.
  • Allow Dwell Time: Allow the coil cleaner to sit on the coil for the recommended dwell time, typically 5-10 minutes. This allows it to break down contaminants effectively.
  • Drain the Drip Pan: While the coil cleaner is working, check and clean the drip pan underneath the coil if it’s accessible. A clogged or dirty drip pan can lead to mold and bacteria growth.
  • Rinse and Drain: After the dwell time has passed, use a spray bottle filled with water to rinse the coil gently. Be sure to catch the runoff with a bucket or towel to prevent damage to the area beneath the coil.
  • Check Drainage: Confirm that the condensate drain line, usually located near the evaporator coil, is clear and not blocked. Clean or clear it if necessary.
  • Reassemble and Restore Power: Once you’ve completed cleaning the evaporator coil and checked for any loose connections or damaged components, reassemble the access panel or compartment and turn the power back on at the circuit breaker.

How to Tell if an Evaporator Coil Needs Cleaning

Cleaning evaporator coils
Cleaning evaporator coils

If your AC is not cooling the house and runs for longer than usual, or when the coil itself it is frozen, you need to clean the evaporator coils. A constantly clogging AC drain line is also another sign of a dirty evaporator coil.

Dirty evaporator coils also causes the blower to work extra hard as it tries to force air through the gunk which also causes an increase in power bills. Sometimes you ca also notice musty/moldy smells coming from the coil or air vents.

If you have never seen an evaporator coil, it looks like an “A” or obverted “V” where copper or aluminum tubes are wound around the frame to form the coil. Radiator-like fins are then installed all around the frame.

When the thermostat calls for cooling, air from the return air duct enters the coil through these fins. Due to the tiny openings, it is very easy for these fins to be plugged by debris from the indoor air.

Dirty coil fins restrict the flow of air from the house to the coil, forcing the unit to work extra hard. Since there will now be less air to be cooled by the refrigerant, you will notice that your AC will not blow cold air in the house.

Also, the imbalance between the refrigerant and air supply, causes the refrigerant’s temperature to drop below freezing point. When that happens, ice starts building up on the coil and after sometime the entire coil will be one block of ice.

I should however add that the evaporator coil can freeze because of other reasons like refrigerant leaks or a dirty air filter. If you notice that your evaporator coil is frozen, turn off the power to the AC and give it time to thaw before cleaning it.

How to Clean an AC Evaporator Coil without Removing It

You will need the following to clean your air conditioner evaporator coils:

  • Screwdriver/cordless drill/socket wrench
  • Commercial coil clean or dish soap
  • Soft-bristled brush
  • Water hose or just a bucket
  • Compressed air can (optional)
  • Flash light (optional)

I would also like to say that you will have an evaporator coil regardless of whether you have an air conditioner or air handler. If you have an air handler, the coil will be located at the top or bottom of the unit but if you have an AC it will be at the top of the furnace.

The following are the steps to follow when cleaning an evaporator coil:

1. Turn off Power to AC/Air Handler

To make sure that you are working safely, start by turning off power to the evaporator coil. It doesn’t make sense to work with blower still pulling air from the house and the refrigerant still cycling through the coils.

Look for a switch near the air handler or furnace which looks like a light switch and flip it to the ‘OFF” position. The air handler or furnace will be located somewhere in the basement, attic, crawlspace or even in a utility closet.

Alternatively, you can turn off power to the AC from the main breaker panel in the house. You should see a double bar (120 volts each) labeled “AC” or “Air Handler”. Pull both bars (could be 1 or 2 separate bars) to the off position.

2. Gain Access to Evaporator Coil

underside of a dirty evaporator coil

The location of the evaporator coil in your cooling system will be different from other houses. Here is how to access the coil:

  • Look for the cover panel. The panel is held in place using screws and the coil is located behind the panel.
  • If there is tape along the edges of the unit (helps to create an airtight seal), start by removing it.
  • Use the screwdriver or drill to remove the screws and keep them and the panel away, in a place where you can’t lose any of them.
  • With the cover panel out, you should now see the evaporator coil. Take your time to inspect the coil and determine the extent of the debris clogging it.
  • In some case, you may need to remove a lower access panel, to give you room to inspect and clean the underside of the A-frame. That may also involve removing the air filter and or disconnecting the return air duct.

You see, an evaporator coil has the outside part and the inside part. You need to clean both sides and not just the outer one. By removing the lower panel/cover and disconnecting the return air duct, you get a good access to the inner part of the coil which is usually the most clogged up.

That also depends on whether you have a vertical HVAC unit (located in basement where coil is above the furnace or air handler) or horizontal HVAC unit (located in attic where the coil and furnace or air handler are connected side to side).

If you have a horizontal HVAC unit, you will need to remove the return air duct in order to access the evaporator coil.

2. Brush Away the Debris

If you are going to use a brush to clean your evaporator coil, you need to be careful, otherwise you can damage your coil:

  • Always use a brush with soft bristles (like a toothbrush) to prevent damaging the fins. Bent fins will restrict the flow of air to the coils and will have the same effect as a dirty coil and that is why a wire brush is not recommended.
  • Brush in the direction of the fins.

The brush will help to remove the large and loosely held debris from the fins. Make sure that you pick up the debris and trash it to prevent it from clogging the AC drain line.

After brushing the inside and outside of the coil, wipe it clean (along the direction of the fins as well) using a wet towel or rag. That will also get some of the dirt out.

If you don’t want to use a brush, use compressed air to blow out the debris from the fins. Compressed air actually clears the dirt very well.

3. Spray the Cleaner on the Coil’s Fins

cleaning the evaporator coil

You have the option to use a commercial cleaner or a homemade one. If you decide to go with a homemade cleaner. Just fill a spray bottle with warm water and then squirt a generous amount of dish soap in there.

Spray the cleaner all around the evaporator coil. Commercial cleaners will foam over the coil and start pulling out the gunk embedded in the fins. Homemade cleans do foam as much bust still do a decent job.

Wait for about 5 to 10 minutes before rinsing off the cleaner.

4. Rinse Off the Coil

Commercial coil cleaners are marketed as no-rinse or self-rinsing so this step is optional. How that works is that once the coil starts cooling the air, condensation will occur and the condensate will rinse the coil.

I however prefer rinsing the coil especially if I used a homemade cleaner. Rinsing off the coil allows you to see if the coil is properly cleaned and if there are spots which you need to clean again.

You can use a hose to rinse the coil or just use a bucket and cup. The important thing to do here is to rinse from the top and work your way down.

There is drip pan located under the evaporator coil. That is where the condensate drips in and is then drained outside. As you rinse the coil, the water will drip in the pan as well so it helps to rinse it in small bursts to avoid overflowing.

You should however have towels or rags nearby just in case the drain is clogged or some water spills on the floor. That is also a good time to clean the AC’s condensate drain line which also tends to clog up. Check out this post on how to clean it.

5. Let the Coil Dry

  • If the coil is not as clean as it should, you can always repeat the cleaning process until you have removed out all the gunk. However, if the coil is clean then wait for some time for it to dry.
  • After the coil has dried, put back the cover panel the same way you removed it. If you removed the filter or disconnected the ductwork put them back as they were.
  • Turn on power to the AC and check if the cooling in the house has improved.
  • Repeat after one year or sooner depending on where you live.

And basically that is how to clean an air conditioner evaporator coil. In this post, I focused on how to clean a central air evaporator coil. If you have a split AC and want to know how to clean its coil, check out this video.