HVAC Repair Tips


All Air conditioners and HVAC systems have evaporator coils that allow the refrigerant to flow through them for cooling or heating the home. If your AC is not cooling and you suspect that your AC evaporator coils are leaking, look for the signs and also know the causes of the leaks so you can prevent them. After determining the leaks, consult air conditioning repair services for fixing or replacing the coils.

AC Evaporator Coils

Evaporator coils and condenser coils are two types of coils that perform the heat exchange process for cooling or heating. In central heating and cooling systems, evaporator coils are present in the air handler unit and the condenser coils are located in the condenser unit (outdoor unit) of the HVAC system.

It’s worth mentioning the location of evaporator coils is different in mini-split ACs. They are present inside the indoor unit or wall-mounted unit of a mini split air conditioner.

Wherever the evaporator coils are located, they are near the blower fan. Evaporator coils have cool refrigerant. This creates cool air that is blown inside your house through ducts or directly through the air handling unit mounted on your home’s wall or ceiling.

Causes Of AC Evaporator Coil Leaks

Corrosion Due To The Formation Of Formic Acid

Evaporator coils are commonly made of copper. Over time, the copper tubing corrodes due to the formation of formic acid on the coils. Formic acid is formed with the presence of water and VOCs buildup on the coil with oxygen.

Water builds up on the coils due to excessive humidity and the function of the evaporator coils. VOCs stick to the coils because they are present in many chemical products and household items like cleaners, air fresheners, pesticides, flooring materials, dry cleaning, and others. Keep in mind that VOCs (Volatile Organic Compounds) are in the form of gas and emit from some solids and liquids that are usually made chemically. They also have adverse health effects on humans.

When formic acid is formed on the coils, it corrodes them and causes pinholes in the coils. These pinholes allow passage for the refrigerant to flow through the coils and cause the refrigerant to leak.


Although the most common cause of leaking evaporator coils is the formation of formic acid on the coils, another reason for pinholes in evaporator coils is AC vibration.

The components and evaporator coil vibrates when the AC is functioning. The evaporator coils have aluminum fins that rub on the coil due to vibration and cause holes in the tubing.

Signs Of Leaking AC Evaporator Coils

Many signs of leaking evaporator coils are similar to the signs of a leaking refrigerant because a leak in evaporator coils results in the leakage of the refrigerant and a refrigerant leak is commonly due to the pinholes in evaporator coils.

AC Takes Longer To Cool The Home

The flow of refrigerant in the evaporator and condenser coils ensures cooling when you have set your HVAC system to cooling. If evaporator coils are leaking refrigerant, the levels of refrigerant will become insufficient for proper cooling. Due to this fact, your air conditioner will require more time to cool the house than before.

AC Doesn’t Cool At All

When the refrigerant levels keep dropping due to the holes in evaporator coils, the AC keeps taking more time to cool the house. However, at a certain point, your AC will give up and won’t cool the house at all. You will notice that your AC is only blowing warm air even when you have set the temperature lower than the room temperature.

Frozen Evaporator Coils

As leaks in the evaporator coils allow refrigerant to leak, this can cause ice buildup on the coils. This is because the leakage reduces the refrigerant levels and low refrigerant makes the coils colder than usual. It leads to the evaporator coils icing up.

However, keep in mind that dirty evaporator coils can also lead to frozen coils. So, if your evaporating coils are freezing up, have them cleaned and if they still ice up after cleaning, they are leaking.

Water Leaks

Low refrigerant causes frozen evaporator coils. When the ice melts, the drain pan of the AC overflows and leads to the unit leaking water. In the case of a mini split AC, the indoor unit will leak water.

The first thing to check if your AC is leaking water is a clogged drain pan and pipes. Clean the pipes with a vacuum or a brush because obstruction in the pipes can cause water leakage as well.

But if you notice water leakage after cleaning the drain pan of the AC, your evaporator coil may be freezing up, then the ice is melting and resulting in water leakage.

You Have To Add Refrigerant To The AC

The refrigerant in your AC is not consumed by the AC because it’s used for transferring warm and cool air in a sealed system. So, the refrigerant aids in cooling and have the same levels as when the AC was installed if there are no leaks.

As you never have to refill your air conditioner with refrigerant, if your AC expert tells you that your AC should be recharged with refrigerant, it shows that the refrigerant is leaking. Commonly, the place where leaks occur is the evaporator coils due to corrosion. However, improper AC installation can also cause refrigerant leaks.

AC Doesn’t Respond To Temperature Changes

Typically, when you lower your thermostat settings, the AC increases the cooling to reach a lower temperature. However, when the evaporator coils are leaking refrigerant, your AC can’t cool effectively. Therefore, even if you lower the temperature more, you won’t notice any change in the cooling. In many cases, your AC will only blow warm or mildly cool air

If your AC is not responding to temperature changes, check the thermostats. If the thermostat is fine, low refrigerant may be the reason for this problem.

High Electricity Bills

Mostly, leaks in evaporator coils are noticed during annual inspections or when the AC stops cooling altogether. The cooling of the AC is impacted when the refrigerant becomes low. As the holes in evaporator coils are tiny, low levels of refrigerant to the point of noticeable impact on the AC’s performance takes time. During this time, your AC works harder to meet the cooling requirements. Due to this, it uses more energy.

Therefore, if you notice that your energy bills are creeping up without any additional usage from your end, your AC is not functioning properly and the coils may be leaking refrigerant.

Hissing Sound From The Unit

If you hear a hissing sound coming from the unit, it can be due to a leak. So, have an expert inspect the unit. If you visually inspect the evaporator, you will see signs of corrosion on the coils. Corrosion is in the form of a spot of rust in one or many parts of the coil. Corrosion on the coils will prove that the coils are leaking.


Leaks in evaporator coils directly impact the cooling ability and efficiency of your air conditioning unit. Get in touch with an HVAC repair service Chantilly for sealing the pinholes in your AC’s evaporator coils. However, the best approach is to replace the coils.


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