Why Is There An Ice Build Up In Your Evaporator Coil?

What is an Evaporator Coil?

The evaporator coil is the component in your aircon unit that absorbs the heat from the air inside your home. It is often either attached to your furnace or located on the inside of your air handler. It works with a condenser coil to complete the heat exchange process that produces cool air.

How does it work?

The evaporator coil is full of evaporated refrigerant that the compressor pumps to the metering device as a liquid then into the evaporator. The air that is pushed through the coil from the blower fan will move over the coil where the refrigerant in the evaporator will absorb the heat.

Why is a clean Evaporator Coil important?

Keeping your evaporator coil clean and well-maintained is crucial to maintaining the efficiency of your aircon unit. Dirty coils can increase the energy use of your aircon unit by up to 30 percent. Poorly maintained coils can also cause other problems with the system, such as poor cooling performance due to reduced heat transfer, frozen coils, and an overheating compressor.

Why is Ice Build Up in the Evaporator Coil a problem?

The process of cooling the air is very delicate and can be thrown off very easily. Refrigerant enters the coils in liquid form and under a great deal of pressure. There, it shifts back to gaseous form, which pulls heat from the surrounding air. The gaseous refrigerant returns to the start of the cycle to start the process again, in which the aircon unit’s fan blows the cool air through the ducts to lower the temperature in your house.

When that process is out of whack, frost or ice will form on the coils, which is problematic in two ways:

1) It represents lost cooling potential which should be going into your home, forcing the aircon unit to work harder to do its job.

2) It forms a barrier of insulation between the refrigerant and the air it’s supposed to cool.

Top causes of Ice Build Up in the Evaporator Coils and Its Solution:

1) Dirty Evaporator Coils

If dust and dirt build-up around the evaporator coils, which transfer refrigerant to the heat pump, it will put extra strain on your aircon unit to condition the air, putting your evaporator coil at risk of freezing. The coils need to be cleaned periodically for proper heat absorption to occur; otherwise, the coils may just freeze over.

This is another reason why it is important to schedule annual professional maintenance so your aircon unit will be cleaned and inspected in order to avoid potential problems like this one. Better yet, join a home maintenance plan so you never forget this important home maintenance task.


Schedule professional aircon unit maintenance once a year to avoid these sorts of problems. You can also DIY clean your entire aircon unit, including your indoor air handler’s evaporator coils. 

2) Refrigerant Issues

Since refrigerant, most commonly Freon, runs in a closed system, you shouldn’t have to replace your refrigerant unless there is a leak somewhere in the system. Although leaks coming from regular wear and tear are common, they sometimes go unnoticed for long periods of time. Running your aircon unit with low refrigerant levels creates unnecessary strain on your aircon unit and can cause ice to build up, on your evaporator coils.


There really is no DIY way of doing this, so your best bet is to call in a professional aircon servicing company to inspect your system for leaks and restore your refrigerant levels. If you don’t address the underlying leak, you will simply run into the same problem again soon.

3) Airflow Problems

You may have a frozen evaporator coil because there is improper airflow from your blower. This can happen for a number of different reasons, but most often involves a dirty air filter.

Other causes of insufficient airflow include:


Although you may need to have repairs, cleaning, and/or maintenance to fix this issue, most airflow problems can be eliminated with a DIY cleaning and air filter replacement. For optimum efficiency, a professional aircon servicing company recommends replacing your air filter every 30 days during peak use. A good test to see if you need to replace your air filter is to observe if light can shine through the filter or not. Set phone and calendar reminders as an extra precautionary measure to remember this important home maintenance task.

The other thing you should check for is proper airflow through your supply and return vents and registers. Although you may have heard it is a good idea to close off vents in unused rooms to save money, which is not a good idea at all. In fact, you should go around your home and make sure that all vents and registers are unblocked. Look behind furniture, underneath rugs, and behind heavy drapes to make sure that airflow isn’t being blocked this way.

4) Inside and Outside Temperatures

Your heat pump and the air handler will not function very well when outside temperatures are too cold.  Sometimes, the evaporator coil will freeze if the aircon unit is running when it’s cool outside.


Diagnose your thermostat for any obvious problems. Try to avoid using your aircon unit at night when the temperatures drop. It is recommended to set your programmable thermostat to 78 degrees or higher while at home and 84 degrees or higher while away from home. Setting your thermostat too low, especially when it isn’t that hot out, can cause your system to malfunction and freeze up.

5) Drainage Problems

Especially on hot summer days, your evaporator coil will have to work extra hard to get rid of all that humidity in the air. When the humidity is removed, condensation forms and is drained away from your home. This is fine, except when you have a clogged drainpipe, which can cause the water to top back up and freeze on your evaporator coils. The frozen condensation further exacerbates the problem.


In order to fix this problem, you will need to unclog your drain pipe. This can be done easily by calling in a professional aircon servicing company, however, there is a DIY method you can try. While you were inspecting and fixing any airflow, refrigerant, thermostat, and drainage problems, your frozen evaporator coils should have defrosted by now.

Once it is completely thawed, turn your system back on and see if any of your DIY troubleshooting solved the problem. If not, don’t worry, it probably isn’t your fault. Most likely, you have a refrigerant leak that needs to be checked out by a professional.

About 338aircon.sg

It’s always a good time to talk about the common issues that aircon units have. This way, you’ll be able to spot if there are problems with your unit or not and prepare for its replacement accordingly. If you require our aircon servicing services, Whatsapp us at +65 9222 4141 for a fast and transparent quote.

338 Aircon Servicing Singapore provides an extensive range of Aircon Services including Aircon Servicing, Aircon Repairs, Aircon Installation of the best aircon brands, Chemical Overhaul, Gas Top-up, Aircon Leaking Water, and Aircon Not Cold Fix, and more. We have a team of professional technicians who are equipped with vast knowledge and experience in the Aircon industry. 

We have over 15 years of experience in dealing with aircon works and have completed thousands of aircon works for both residential (Landed, Condo, and HDB) and commercial. We are a highly recommended Aircon Company in Singapore, with many delighted customers and reviews over the years on Google and Facebook. 

WhatsApp us at +65 9222 4141 for a transparent quotation and honest pricing for all your aircon needs or Call us at +65 9222 4141. We offer a fast and efficient service to serve any of your aircon needs!