Why is My AC’s Evaporator Coil Half-Frozen?

Your air conditioner works hard throughout the summer months to keep your home cool and comfortable. Unfortunately, even the most well-fitted, durable air conditioner can have difficulty operating properly throughout the summer months.

One common issue for homeowners is to find their AC evaporator coil half-frozen.

If your AC has been performing oddly, an examination may reveal the evaporator coil half-frozen.

However, if you are unfamiliar with the internal workings of an AC, you may be wondering what an evaporator coil is or how to discover if half of the evaporator coil is frozen.

Here are answers to all your evaporator coil questions, including why only the bottom half of your evaporator coil is cold.

What is an Evaporator Coil?

The evaporator coils are an integral part of the cooling process in your AC unit.

They allow your air conditioner to exchange hot air into the cold air, then blow that cool air throughout your home’s vents. Finding your AC evaporator coil half-frozen depends on your ability to locate the evaporator coil in the first place.

If you’re hoping to check to see half of the evaporator coil frozen, look inside your unit near the air handler. The evaporator coils are usually close to the fan blower. 

As warm air collects in your home, it passes over the evaporator coils which hold liquid refrigerant. During this process, the liquid refrigerant turns into gas, cooling the air.

Your AC unit’s blower then pushes the cool air throughout your home, making the indoor temperatures comfortable. If you find your evaporator coil half cold, there could be a few reasons why.

Signs the Evaporator Coil is Half-Frozen

If you aren’t sure how to tell if only the bottom half of my evaporator coil is cold, here are a few signs indicating it is half-frozen:

  • Your AC won’t turn on.
  • There’s a refrigerant leak near your AC unit.
  • Warm air is coming through your vents.
  • The AC stops and starts frequently throughout the day without cooling your home effectively.
  • Banging or hissing noises are coming from your AC.
  • Strange smells coming from your AC.
  • There’s ice around your refrigerant line.
  • Half your evaporator has condensation or ice on it.

What Causes Half of the Evaporator Coil to Freeze?

Below are the most common reasons homeowners find themselves with a half-frozen evaporator coil.

Dirty Evaporator Coils

When your AC unit’s evaporator coils are dirty, they are much more likely to freeze over. If you notice your evaporator coil half-frozen, that could mean that only half the coils are dirty.

As dirt and dust collect on the coil, it cannot release or absorb heat which causes it to freeze over. Keeping your AC’s evaporator coils clean and dust-free can help prevent this problem from occurring. 

Leaking Refrigerant

Refrigerants are a potent means of cooling your home’s air. However, if your evaporator coils don’t have enough refrigerant in them, they won’t be able to absorb the heat from the air and will send the AC unit into overdrive.

When that happens, the evaporator coils freeze up. Leaks can quickly cause your refrigerant levels to drop, freezing your coils and causing your AC unit to stop working properly.

Not only will the refrigerant levels need refilling, but the leak will need to be located and repaired to prevent this issue from happening again.

Drain Clog

Dirt, dust, and other debris can collect inside your AC unit as it operates throughout the summer. As condensation forms on the evaporator coils, it’s normal for some moisture to drip.

If the drainpipe in your AC unit is clogged from debris or dirt, then too much condensation can develop. The drain can back up, causing the evaporator coils to freeze. The drain will need to remain clean and fully operational to avoid this problem.

Bad Airflow

If there isn’t a steady supply of air, then your evaporator coils could freeze over. Your whole air conditioner unit performs best with proper airflow, so if there isn’t enough then your air conditioner loses efficiency. Not only that, but your evaporator coils freeze over.

This malfunction is best prevented by keeping your air filters clean, replacing broken fans, and not blocking vents or registers. It’s also important not to pile boxes or other items around your AC unit.

Old Air Conditioner

The sad news is that sometimes an evaporator coil half cold indicates your AC unit is reaching the end of its lifespan. Air conditioners only last so long and problems can only be prevented for a certain amount of time. If your AC unit is older than 10-15 years, it may be reaching the end of its life.

Replacing the unit could be more worth your while than repairing whatever complication caused the evaporator coils to freeze.

How to Fix a Half-Frozen Evaporator Coil

Fixing a half-frozen evaporator coil depends on the source of the problem. Some things are easy repairs, such as changing out the air filter or cleaning the evaporator coils. Other things require professional help, such as replacing the refrigerant levels or repairing a leak. 

Here are the steps to fixing a half-frozen evaporator coil on your own (assuming there aren’t any serious failures): 

Step 1: Allow the Coils to Thaw

You shouldn’t run your air conditioner if the evaporator coils are beginning to freeze up. That can end up causing more damage to your unit. Thaw your evaporator coils by shutting your AC unit off. The coils can take up to 24 hours to thaw on their own. 

Step 2: Change the Air Filter

Dirty air filters are the culprits of many HVAC issues. Before you start your air conditioner again, make sure to exchange the air filter. Replace the old, dirty one with a new, fresh filter. Regularly changing your air conditioner can help prevent your evaporator coils from getting dirty and freezing. It can also preserve the life of your AC unit.

Step 3: Clean the Coils

There’s no point in thawing your coils and changing the filter if you don’t also make sure your evaporator coils are clean. Before starting your AC unit again, check the thawed evaporator coils and make sure they are clean. Before you attempt to clean your evaporator coils, make sure your AC unit is fully off—best to turn it off at the breaker panel.

Consult your unit’s manual if you have difficulty locating the coils. Clean them with regular cleaning liquid or warm water. Wipe with a soft cloth. Once the coils are clean, you can turn your AC unit back on.

Step 4: Call in the Pros

There are many things you can do as a homeowner to preserve the life of your AC unit and even keep your evaporator coils from freezing over. That being said, it’s always safe to trust any AC jobs to the professionals. Working with a licensed HVAC technician gives you the peace of mind that the job is done correctly. A skilled professional will also be able to spot any other issues in your unit and correct them before they break down.

Preventative Maintenance is Key

preventative maintenance plan can help keep your evaporator coils from freezing before they even start icing over. While there is a lot of normal wear and tear on your AC unit as it runs, some malfunctions are lessened when your unit is regularly cleaned and maintained. Schedule your AC service with John C. Flood to repair frozen evaporator coils or to prevent breakdowns. 

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