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Why Is Your AC Freezing Up?

It’s a sweltering summer day, and you depend on your air conditioning unit’s sweet, cool air to save you from the oppressive heat. But what happens when your AC starts to freeze up? Suddenly, that cool air you were depending on is gone.

Don’t worry, you’re not alone. Air conditioners freezing up is a common problem that can be caused by a variety of factors. In this guide, we’ll explore the reasons why your AC might be freezing up and what steps you can take to fix the issue.

How an AC Works

Before we dig into what causes your AC to resemble an ice cube, it’s crucial to wrap our heads around why this issue isn’t just a matter of annoyance—it’s a potential red flag for your system’s health.

Understanding the workings of an AC unit is key to recognizing why it might freeze up. At its most basic, your air conditioner absorbs the warm, moist air from your home, cools it by passing it over refrigerant-filled coils called evaporator coils, and then circulates the cool air back into your living space. This process relies heavily on a fine balance of airflow and refrigerant levels. Because removing moisture from the air is a normal part of your AC’s job, when either airflow or refrigerant get out of sync, trouble begins.

Primary Causes of AC Freezing

Eliminating heat causes the evaporator coil to become extremely cold. The only factor preventing the evaporator coil from freezing is the warm air that the blower motor draws in as it expels cold air.

In situations where airflow is restricted

  • the evaporator coil becomes exceptionally cold due to an insufficient amount of warm air flowing over it
  • moisture (humidity) present in the air comes into contact with the evaporator coil, condenses on its surface, and then freezes, leading to a freeze-up of the AC coil

A Sign Something is Wrong

When the components within your air conditioner start to freeze up, it’s not just about the inconvenience of not having a properly functioning cooling system. The reasons behind this phenomenon often point to underlying issues within the AC unit’s balance that can lead to costly repairs if left unchecked. Worse still, ignoring regular freezing can lead to the premature demise of your AC unit and the replacement costs that come with it.

Signs Your AC Unit is Frozen

There are several signs you can look for to determine if your AC has stopped working because it has frozen:

  1. Visible Ice Formation: One of the most straightforward indicators is the presence of ice on any part of the HVAC unit. This includes ice accumulation on the external condenser unit, refrigeration pipes, or the copper lines coming out of the system. In some cases, you might also notice frost build-up on the copper lines.
  2. Lack of Cool Air: If your AC system fails to reach the desired thermostat setting or if you feel warm air blowing from the air registers instead of cool air, it could signify that the unit is frozen.
  3. Water Leakage: When an AC unit freezes and then starts to thaw, it may result in water leaking from the unit. This could be a sign that ice had formed on the coils or other parts of the system.
  4. Poor Airflow: Another symptom of a potentially frozen AC unit is significantly reduced airflow or complete cessation of air blowing through the vents. This could happen when the evaporator coil inside the unit freezes up.
  5. Condensation: While not as obvious as ice formation, excessive condensation around the unit or on the refrigerant lines can also indicate that the AC is freezing up.

Pro Tip: It may be tempting to chip off the ice, but it is best to let it melt on its own. Chipping it off can damage lines and other AC components and there is no need to create more repair headaches.

Bonus Pro Tip: You may need to babysit your AC as the ice melts to avoid overflowing your drain pan and causing damage to floors.  Periodically, check for ice blockages and be ready with towels for overflows.

Reasons for AC Freezing Up

For an air conditioner to do its job, it must achieve a delicate balance of airflow, refrigerant, and temperature control. When one of these factors goes awry, the result is all too often an icy buildup on its coils.

Here, we uncover the top culprits and offer the solutions you need.

1. Low Refrigerant Levels

Without the appropriate refrigerant levels flowing through it, your AC can’t effectively remove heat from the air. Consequently, the system’s evaporator coil can chill well below freezing, causing any moisture in the air to freeze on its surface. This thermodynamic hiccup can lead to a full-blown block of ice within your unit, hindering proper operation.

Solution: The fix here is to have a professional HVAC technician locate and repair any leaks in your system. It’s crucial not to simply “top off” refrigerant levels as a temporary solution—true resolution means addressing the leaks head-on.

2. Dirty Air Filters

Your AC’s air filters are the unsung heroes of your home’s air quality and system performance. When these filters become clogged with dust, dirt, and pet dander, they restrict the airflow over the evaporator coil.

Solution: Make a habit of checking and changing your air filters regularly – ideally every one to three months. It’s a simple DIY task that can save you from many AC headaches and keep your unit running efficiently.

3. Blocked Airflow

Any obstructions in the vents or around the AC unit can lead to a buildup of cold air within the system. The lack of warm air passing over the evaporator coil essentially tells your AC to keep going until it reaches zero.

Solution: Keep furniture, curtains, and anything that might inadvertently block your vents away from your AC system.  Don’t close too many vents at a time. Also, ensure your outdoor unit has proper clearance for air to circulate by keeping away plants, trees and other obstacles to airflow.

4. Thermostat Malfunction or Set Too Low

Your thermostat is the brain of your AC, giving it cues as to when to turn on and off to maintain comfortable indoor temperatures. However, if your thermostat isn’t working properly, it might instruct your system to  keep running even when your home has reached the desired temperature.

Additionally, if you set your thermostat too low or it isn’t the right size for your home, your AC will continuously run in an attempt to reach that temperature, putting unnecessary strain on the system.

Solution:  Check to make sure your thermostat is set to “cool” and not just “fan.” Make sure your thermostat is set at a reasonable temperature to avoid overworking your AC. Also, check your thermostat’s batteries and replace them if needed. If it continues to malfunction, consider having a professional inspect and potentially replace it. It might be time for an upgrade to a programmable or smart thermostat, which can save you money on. 

5. Issues with Evaporator Coils

You could have the cleanest air filters and an unobstructed air flow, but if the evaporator coils inside your AC are dirty or damaged, that’s a recipe for a freeze. Coils caked in grime can lead to a barrier insulating the coil, similar to how a dirty air filter can block airflow.

Solution: This is another issue that is best left to professionals. Regular maintenance should include checking and cleaning the evaporator coils to keep them in optimal working condition.

Solutions to Prevent Freezing Up

Understanding the causes of AC freezing is half the battle. Knowing how to prevent these frosty fiascos can keep you cool-headed and comfortable all summer. Here are some proactive steps you can take to avoid your AC turning into an ice sculpture:

Regular Filter Checks: Monthly checks on your air filters are a breeze (no pun intended) and can do wonders for your AC’s health.

Keep It Clean: Dirt is the enemy of efficiency. Keep the area around your AC free from debris, and schedule regular professional cleanings to keep all components in top shape.

Thermostat TLC: Treat your thermostat with respect. Keep it away from temperature-influencing factors and maintain the power it needs to operate smoothly.

Annual Inspections: An ounce of prevention is worth a pound of cure. Having an HVAC technician inspect your system annually can catch potential issues before they escalate.

AC Maintenance in Portland

Your AC is a modern marvel capable of turning the hottest day into a tolerable retreat, but it isn’t invincible. Understanding why it might freeze up empowers you to take action and keep your system running optimally for years.

If you are looking for help troubleshooting your air conditioning system, our consultants at Jacobs Heating & Air Conditioning can examine your system and determine what repairs need to be made. If you need air conditioning maintenance, we are ready to help you save money and keep surprise breakdowns away. You can schedule your next tune-up and take the stress and hassle out of maintaining your system. No matter what you need, we’re always just a phone call away