Understand What Is An Evaporator Coil And How To Fix Common Problems

Many of the most common problems that can go wrong with air conditioners have to do with the evaporator coil. If you understand what the evaporator coil is and how it works. In that case, you will probably be well on your way to understanding, diagnosing, and fixing your air conditioner unit, as well as prolonging its lifespan and efficiency.

What is an Evaporation Coil?

Let’s begin with the basics and go over what precisely an evaporator coil is. An evaporator coil is an integral part of the air conditioning unit. It is essentially the component that provides cool air.

The coil is usually placed in the interior of the air conditioning unit. It is easily recognizable since it looks like a car radiator. It has the basic function of absorbing heat and therefore cooling your home, but we will get more into details in the next section.

Location of evaporator coils in your air conditioner

These coils will be located within the indoor aircon unit. The evaporator coil is used to hold the chilled refrigerant that is moved through it by the compressor and can be found within the blower compartment. 

How does an Evaporation Coil Work?

The coil is filled with a cooling refrigerant that flows throughout the system. Once the coolant reaches the evaporator, it is in the consistency of eighty per cent liquid and twenty per cent vapour. As it makes its way through the coil, it accumulates hot air from the air that is flowing over the evaporator coil.

The effect is that of latent heat transfer. If you are wondering what that is, you are not alone. Latent heat is also known as the heat of transformation. It refers to the heat that a unit of mass evaporates. In the process of evaporation, no change in temperature is recorded, but the heat is transformed to vapour.

Once the cooling refrigerant is transformed completely into a vapour state, it then goes through a process of superheating. Once the vapour makes the full cycle back to the compressor and goes through the condenser, it is transformed back into the original consistency of eighty per cent liquid and twenty per cent vapour. Once again, being a low-pressure refrigerant, it can start the process all over again, continuing to cool the air that passes through the air conditioning unit.

What are the signs for a bad evaporator coil?

At times, homeowners feel their air conditioner is not functioning as it should and causing indoor conditions to be uncomfortable. This requires the attention of an AC technician who can repair air conditioners. You will notice sure signs that indicate that your evaporator coil or its components are damaged, that can include:

What is the cause for evaporator coils going bad?

One of the most common causes for leaks in evaporator coils is the corrosion of its copper tubing. Your indoor air can contain volatile organic compounds (VOC). When this interacts with water and copper, it leads to the formation of formic acid, which, when it accumulates, can corrode the copper.

What Are The Common Problems with an Aircon Evaporator Coil?

Now that you have a basic grasp of what an evaporator coil is and how it works, you are ready to troubleshoot it. We will now go through some of the most common problems that an evaporator coil can have.

We will also give some advice on fixing the most common problems. However, in the case that it is better to let an aircon repair professional do the work, we will also advise you.

Problem 1: Frozen Coils

If an evaporator coil freezes, as strange as it may seem, it will interfere with the unit’s capacity to cool down the air that passes through it. While this may seem counterintuitive, the reason is that the coolant inside the coil is supposed to absorb the hot air outside the coil. If there is a film of ice on the outer tube, it acts as an insulant; therefore, it does not allow the hot air to be absorbed. In this case, the unit will continue to run, but without the cooling effect that we so desire.

How to Fix a Frozen Coil:

Find what is limiting the airflow in the unit. When proper airflow is restricted or limited, it throws off the balance that the system depends on.

Start with the most obvious: make sure nothing is blocking the airflow into the unit and check for kinked or damaged tubes, especially if you are dealing with a window unit that has recently been installed. Another common reason for restricted flow is that the refrigerant level is low, so check the level and make sure it is adequate.

Problem 2: A Leaky Unit

Leaks usually occur in the coil. If there is a leak, this will obviously throw the system off balance. It will make the unit have to work much harder, causing additional pressure on the AC unit, eventually causing other problems.

If you have a gas leak in your air conditioning unit, do not procrastinate in getting it fixed. Cooling refrigerant is a poisonous chemical compound that should not be breathed or touched as it can cause respiratory problems as well as damage to the skin. In addition, it is dangerous to animals and the environment.

In addition to all of that, it will also damage your AC unit. Leaks will corrade the outside of the coils. It will also cause wear and tear on the coil limiting its lifespan.

Thankfully leaks are easy to spot. If you do spot one, it is better to contact a specialist to deal with it rather than trying to fix it on your own.

Problem 3: Dirt and Debris

While this seems like an obvious problem, it is surprising how many units are out there suffocating under the pressure of dirt and debris. As you can probably see after what we have considered so far, a dirty coil can not properly perform its duties. It is true that a little bit of dust will not adversely affect it. However, too much dirt will insulate the coil, and, similar to ice formations, it will not allow the coil to absorb the heat properly.

How to Fix a Dirty Coil:

Thankfully it is a very easy fix and one that should become part of its regular maintenance. The first step would be to remove any debris that has accumulated. Leaves, grass, and stray plastic bags are examples of debris that are commonly found around the coils.

As far as actually cleaning the unit, there is no shortage of advice out there on how to do this, but it basically boils down to having a hose, a good spray cleaner, and a good brush. Spray the coils down and use a delicate brush to gently brush the coil. Hose the coil down to finish and then restore power to the unit. If you do this at least once each season, you will prolong your unit’s life and efficiency, and you will also reduce running costs.

Is it possible to repair evaporator coils?

Yes. It is possible to repair evaporator coils, but often replacement is the preferred option.

Many components in a cooling system require simple repairs, but it is a little more complicated in the case of leaking evaporator coils. Over time, there is erosion in the coil’s inner lining, which weakens the metal. The outer part of the lining can also corrode, leading to further damage. The coil is then very susceptible to forming leaks.

Refrigerant leaks from within the coil can be repaired, but replacement of the coil is the preferred solution. In the long run, this can turn out to be less expensive than the cost of repairs, as every time you have to do this repair, you also need to recharge the system with fresh refrigerant.

When should I replace my AC evaporator coil?

A leaking evaporator coil needs to be replaced. Repairs can be cheaper, but it is a fix that may not last for a long time. A repaired coil will only bring back its performance efficiency to between 50 and 75 per cent. 

What is the difference between an evaporator coil and a condenser coil?

Condenser coils and evaporator coils have a similar design. Their functions, however, are entirely opposite to each other. An evaporator coil picks up heat from the air inside, while a condenser coil releases the heat to the air outside.

Heat energy load that is removed from the home, and is in compression in the hot vapour, will get released as soon as the refrigerant circulates in the coil and is condensed into a liquid.

As this heat load is released by the refrigerant, a fan in the unit blows it through the passages in the condenser coil and disperses it into the surrounding outside air.

Related Read: The Main Difference Between The Condenser Coil And The Evaporator Coil In Your AC

How do you clean an evaporator coil without removing it?

  1. Switch off the thermostat in the AC.
  2. Remove the panel that can give you access to the evaporator coil.
  3. Buy a spray cleaner can, one that does not require rinsing and has clear instructions. Spray this cleaner on the evaporator coil.
  4. Stubborn debris can be removed by using a gentle paintbrush or nylon brush.
  5. Once the coil is cleaned, the access panel can be replaced, and the AC turned on.  

If you can follow these simple steps, do so; otherwise, call your AC service provider to get this cleaning done.

Is it normal for evaporator coils to be wet??

Evaporator coils also dehumidify the air by collecting moisture from it. Typically, this moisture inside the home will gather on the evaporator coil and drip down into a drain pan located just below it.

How long do AC evaporator coils last?

Regular maintenance of an AC can allow an evaporator coil to live its full life span. This, with regular maintenance, can be as long as 10 to 15 years and compares well with the ideal lifespan of the AC unit itself.


We hope you found this article informative and helpful. If you have any questions, need help replacing your evaporator coil or want to schedule a service call with our team of experts, contact us today. Our technicians are always happy to answer your questions about AC Evaporators!

Related Read: 2 Types Of Air Conditioner Coils And How These Coils Work

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