How to tell if the evaporator coil in your air conditioner is broken

Evaporator coil leaks or breakages in your air conditioning can be hugely frustrating and, if not detected quickly, expensive to fix.

To help you avoid paying hefty fees for a new evaporator coil, we put this guide together. 

Here, we explore the common reasons for broken or leaking evaporator coils, what causes them, and, most importantly, what you can do to mitigate the risk of needing an evaporator coil replacement.

What is an evaporator coil?

An AC evaporator coil is typically located near the system fan in the indoor unit of an air conditioner. The coil is made from metal, usually copper, aluminium or steel, as these conduct heat well. In terms of what it looks like, the evaporator coil features a series of tubes that wind around A-shaped panels. These panels are also lined with thin pieces of metal, which maximise the cooling by guiding passing air into the coil.

What does the evaporator coil do?

The evaporator coil plays a vital part in the cooling process of your air conditioning unit. The coil cools the refrigerant to absorb the heat from your home. If this component becomes broken or faulty, and your air conditioning no longer blows cool air, it can be very frustrating. 

Want to learn more? Read our ‘What is air conditioning refrigerant’ guide.

So, the evaporator coil in your air conditioning system has stopped working. This can leave you uncomfortable and stressed. But don't panic - we put together this handy guide to help you out with any issues your evaporator coil is having. 

Common evaporator coil problems

Before we get into the ins and outs of evaporator coils, their common faults, and what might have caused them, here are some telltale signs that you have a broken or leaky evaporator coil:

• Your air conditioning won't turn on  
• The vents are blowing out warm air
• Your air conditioning system starts and stops frequently
• The refrigerant is leaking
• Unusual noises are coming from the units
• There is an increase in your energy bills - this may indicate that the air conditioning unit is having to work harder to cool your home

In terms of fixing issues, you should only attempt to repair leaks or a broken evaporator coil if you're a trained HVAC professional. Otherwise, you risk voiding your air conditioner's warranty and exacerbating the issue, making it more expensive to fix.

1. Leaking evaporator coil

If your evaporator coil starts leaking, your air conditioning system will need to work a lot harder to cool the air, which can cause it to break down. 

This may happen in older air conditioning systems; however, if a leaking evaporator coil occurs when your system is relatively new, this could be due to a manufacturing defect or a poorly installed coil. 

A leaking coil should always be replaced, not repaired, and you should call a professional to fix this.

Leaky evaporator coils are more common in older air conditioners and mean that the system will have to work a lot harder to cool air. Ultimately, leaking coils can cause air conditioning units to break down unless the problem is rectified quickly.

What causes evaporator coil leaks?

These things commonly cause evaporator coil leaks:

• A reaction that can occur when copper, water, and volatile organic compounds combine to create formic acid, corroding the copper tubing
• Holes in the pipes that form due to excessive vibrations from aluminium fins
• A build-up of mould that weakens the pipework

An evaporator coil leak can happen when dirt and debris are left to build up, making it essential you have your air conditioning unit serviced regularly, especially before the warmer months when you'll rely on your cooling system most.

2. Frozen coils

If your evaporator coil is frozen, you'll find ice forming around the coil. Luckily, this issue can be repaired, so you won't need to pay for a new evaporator coil.

Although thawing AC evaporator coils may be as straightforward as turning off the system and giving it a chance to thaw out, you must inform a fully qualified HVAC technician about the problem so they can inspect any additional damage.

The engineer will also check the system to ensure there are no blockages or refrigerant leaks. Frequent freezing could be a sign that there is a more severe issue with your AC system, so you must get it checked out as soon as possible.

What causes frozen coils?

The common reasons for evaporator coils freezing in an HVAC unit are:

• Low refrigerant levels: Air conditioners need a certain amount of refrigerant to ensure adequate performance. Too little, and the system may freeze up.
• Blocked condensate drain line: The condensate line expels excess water from the cooling system; if this line blocks and water collects near the evaporator coil, it can freeze because it is the coldest part of an AC unit.
• Dirt and debris in air filters and vents: Air conditioners need airflow to function correctly. If a filter or duct is obstructed, e.g. by dirt and debris, the coils may get too cold, accumulating ice.
• Faulty thermostat: Problems with your thermostat may mean it senses the wrong temperature, resulting in over-cooling and, eventually, frozen evaporator coils.

3. Dirt in the coil

A dirty evaporator coil can have a significant impact on the performance of your AC and the air quality inside your home. The following symptoms can all be signs that dirt has built up in the evaporator coil:

• Increased energy consumption
• Reduced performance and capacity
• The unit produces an unpleasant smell

What causes dirt in evaporator coils?

As air passes through your AC system, small dirt particles can be picked up. Once these start to collect, they can remain in the evaporator coil, reducing the airflow performance of your unit.

To manage this problem, you should ensure the outdoor unit of your air conditioner is kept free of obstructions.

4. The refrigerant is running low

As the refrigerant passes through your air conditioner, it cycles between gas and liquid states, being recirculated through the system. So, in theory, the refrigerant should not diminish; however, if the refrigerant does start to run low, the evaporator coil will have nothing to cool, and the unit's performance will suffer.

Low refrigerant levels may also indicate a leak, so if you think your refrigerant needs topping up, you should call an HVAC technician to take a look.

What causes low refrigerant?

A refrigerant leak somewhere in the system may cause the problem. Still, it could be caused by using the air conditioner for extensive periods or in scorching weather, when increased demand puts pressure on the system.

5. The fan has stopped working

The fan is an essential part of the cooling process as it blows air across the evaporator coil. Without the fan, air cannot travel around the system, resulting in problems with the evaporator coil, including freezing.

What causes a broken fan?

Many factors can affect the performance of an air conditioner fan or even break it completely. These include:

• Electrical problems: If you have had your air conditioner for a while, the system's wires may have become frayed or loose, impacting the performance of the motor and the fan.
• Damaged fan blades: The blades on the AC unit's fan may bend or break. This can happen if dirt or debris has built up. If you have tried to fix the system yourself and have not taken the proper care, you increase the chances of damaging the fan blades, so it's best to have a qualified technician inspect your air conditioner.
• Motor issues: If you notice the fan not moving, it could be because the motor has burnt out. This can occur if the air conditioner has been used for an extended period or on an intense setting.
• A blocked air filter: An air conditioner needs good airflow to work at optimal levels. If it becomes blocked, ice can start to collect, putting pressure on the fan and eventually causing a breakdown.
• Broken belt: Some AC units, mainly older ones, run with a belt that connects the motor to the fan. As this component wears, it may slip or break, causing the fan to stop working.

What to do if your evaporator coil is beyond repair

If your evaporator coil breaks, call an HVAC technician to investigate the problem. Sometimes, the system may need a replacement coil; however, it could be more serious.

You should never attempt to replace or fix the evaporator coil yourself, as this may make matters worse. Instead, trust a fully qualified HVAC engineer to inspect and repair the system. 

If you need a new air conditioning unit, contact the team at BOXT for an installation quote.