Why You Have Dirty Evaporator Coil

The AC evaporator coil is responsible for removing the heat from the air and cooling it down. It can get dirty due to the particles, pollens, and dust in the air that it processes. Cleaning your AC evaporator coil can help in maintaining your AC unit’s performance.

Air conditioning units can bring a huge relief during the unbearable hot days of summer. It might get a bit frustrating when the AC suddenly stops working correctly.

The majority of AC problems that consumers encounter comes from malfunctioning, dirty evaporator coils. If you want to avoid getting this problem, you might want to start cleaning your evaporator coil regularly. 

What Does An Evaporator Coil Do?

The evaporator coil the part of the AC that makes the air cool. A blower motor redirects the warm air into the evaporator coil, where it passes through and gets chilled. These processes all happen while the air passes through the evaporator coil. Once the hot air is converted, it will then gets release to the targetted area. 

But how does an evaporator coil cool down an incoming hot air? The coil itself is loaded with liquid refrigerant. AC compressor sends more refrigerant inside the coil to meet the temperature in the thermostat. This process is reversed during the winter, wherein heat is absorbed and retained in the evaporator coil. 

A good airflow towards the evaporator coil is necessary to keep the whole AC unit functioning. The air passing through is not cooled efficiently when there is a blockage that appears in the system. Unfortunately, the evaporator coil can get dirty, and this dirt layer causes air blockage. 

What Causes Dirty Evaporator Coil?

If the only thing that passes through the evaporator coil is air, how can it accumulate dirt layers? The answer to this question is pretty straightforward: dirt and dust particles. We might not see it, but the air has tons of fine dust and dirt particles. These will stick to the coil and cause problems.

There is also other stuff like water vapors, pollens, allergens, and even fine pet hairs. Think of the evaporator coil as a huge filter. It cratches all the dirt, dust, pollen, and other particles in the air. When all of these particles accumulate, a layer of dirt and dust will form. 

Over time, these small particles will form grime and dirt layers. Most HVAC experts clean evaporator coils by removing this component from the AC first because these dirt layers are tough to break. You might need a specialized chemical cleaner if the layer is too embedded in the coils. 

How To Tell If Your Evaporator Coils Are Dirty?

Opening up the AC panel and checking if the evaporator coil is dirty is not the most convenient thing. Unless you’re cleaning it regularly or if you have low-quality indoor air. Poor air quality tends to cause a faster accumulation of dirt inside the coil. However, there are a few external signs as well. 

You might mistake some of the external signs of dirty evaporator coils for something new entirely. Since most of these signs might appear from time to time, people tend to ignore them until it’s too late. If you see two or more signs from this list, you might want to take a quick peek at your evaporator coil. Chances are, the dirt and grime layers are already pretty troublesome. 

  • Warm air coming from the vent
  • AC stops and starts frequently
  • Weird or unusual noises 
  • Refrigerant leaks

An AC owner should be wary of these signs to avoid evaporation coil problems. If the evaporator coil malfunctions or is left dirty for a considerable period, malfunctions can happen. 

What Happens If The Evaporator Coil Is Dirty?

There’s a lot of things that can happen to the AC when the evaporator coil is dirty. And all of these things are bad news. Keeping up a clean evaporator coil is a necessity if you don’t want to experience the following things: 

  • Inefficient cooling – a clogged evaporator coil will not have direct contact with the air. This means that the system needs to work a bit harder to cool down a certain area. 
  • Higher electricity bills – since your system works extra, your power consumption gets increases as well. You might not notice the rise at first, but it will be reflected in your bills. 
  • Possible coil freeze – freezing can happen when the air inflow inside the coil slows down. Due to the airway restriction, the evaporator coil won’t absorb heat efficiently, resulting in the condensation freezing up before it is absorbed.
  • Water or refrigerant leaks – a water leak happens when the ice that forms inside the AC melts after it is turned off, causing pools of water to accumulate. The refrigerant leak occurs when the dirt causes corrosion, causing the coil to break. This kind of leak causes a hissing or gurgling sound (on larger holes.)
  • Early component replacements – problems like the refrigerant leak or widespread corrosion will require you to replace the evaporator coil, which is an expensive purchase. 

Either way, cleaning your evaporator coil should be one of your habits in maintaining your AC unit. Dirt and grime layers can break the system or hamper its daily operations. 

How Do I Know If My Evaporator Coil Needs Cleaning?

The best indicator of a dirty evaporator coil is when there is warm air coming from the vent. It is an indicator that the dirt layer accumulated on the surface is already inhibiting an efficient heat transfer from the refrigerant to the air. 

You should also be aware of ice development in the coil. If this happens, the clog or blockage in the airway might be already too restricting. Ice forms when the condensation in the system freezes because the refrigerant isn’t receiving enough air to cool down. 

And lastly, if your AC system is running longer than usual to reach the preferred temperature, it might be because a clog is restricting it. Although these problems can indicate other components malfunction, check the evaporator coil first can save time and troubleshooting efforts.  

How Often Should I Clean My Evaporator Coil?

The rule of thumb in cleaning the evaporator coil is at least once a year. However, it depends on your location. If you’re living in an area where it’s easy to accumulate dust and other particles, you might have to clean your evaporator coil every couple of months. You might want to consider calling for professional help in your area. 

How Much Is It Needed To Clean Evaporator Coils?

Most HVAC professionals use coil cleaning sprays and other cleaning materials to ensure that all grime and dirt are removed. These sprays use foam to break the accumulated grime and are priced between $5 to $20. It also depends on the can size and other factors. 

However, you can use household items like vinegar and soap for a quick clean. These methods can require you to remove the coil from the AC unit. Start by blasting the coil with compressed air to remove light debris like human and pet hair.

How Do You Clean A Dirty Evaporator Coil?

You can clean your evaporator coil using three methods: coil cleaning spray, soap and water, and vinegar. In all these methods, you might want to start by blasting it with compressed air to remove bigger debris. If there is no compressed air, you can use dog grooming brushes. Before starting, make sure that the AC’s power is completely turned off.

Via Coil Cleaning Spray

Apply the foam spray to the evaporator coil. Make sure that all the coil surface is sprayed with the foam and nothing is missed. Keep the foam for five to 20 minutes (based on the spray’s instruction) before rinsing it entirely with water.

Via Soap, Vinegar, And Water

If you don’t have a coil cleaner available, the best option is the old soap and water. However, you need to remove the evaporator coil from the AC unit because the cleanup will require a lot of rinsing. 

Make a cleaning solution using a few drops of dishwashing detergent and water. Mix it all and spray it into the evaporator coil. Let it sit for a few minutes before using a brush to remove the dirt. For tougher dirt layers, you can double-spray the area until the grime loosens up. 

Using another sprayer, mix half-and-half water and white vinegar solution. Spray this solution to the coil after cleaning it with soap. 

Vinegar is used to disinfect the coils and prevent molds and algae from forming up. Take note that this step will leave your AC to smell acidic in the following days. Better avoid doing this method when you’re receiving a visitor. 


A dirty evaporator coil can cause many HVAC problems like cooling inefficiencies and poor air quality. Since prevention is better than cure, avoid damaging your evaporator coil by cleaning them regularly. If you’re unable to clean your evaporator coil, call for help from the nearest HVAC service provider in your area.