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Why Is My Air Conditioner Freezing Up?

Troubleshooting air conditioner freezing issues

When air conditioners operate under extreme stress, they often ice over and shut down. If your air conditioner has buildups of frost on its evaporator coil or if it’s circulating warm air, it likely has wear or maintenance-related issues. At One Hour Air Conditioning & Heating, we help homeowners save money with effective troubleshooting and timely interventions. That’s why we’re sharing several common reasons why air conditioners freeze up along with tips for mitigating the underlying problems.

Dirty Air Filters

Air conditioners cool homes by transferring indoor heat outside. They do so by drawing warm air over their refrigerant-filled evaporator coils. All of the air that enters your cooling system passes through your HVAC air filter. As your filter grows heavy with accumulated debris, your air conditioner works harder.

Accumulations of dirt, dust, and other airborne particulates create thick, lint-like mats on filter mesh. If you haven’t inspected and replaced your air filter for quite some time, this mat could be too dense for air to flow through.

Not only does this result in warm air coming from HVAC air vents, but it can also cause a noticeable rise in indoor humidity, especially around your air handler. As this extra moisture settles on the evaporator coil, the coil frosts over.

An easy way to determine whether your filter has reached the end of its lifespan is by holding it up to the light. If light can still pass through a filter’s mesh, air can as well. To prevent filter-related freezing, be sure to check this component at least once each month. According to most HVAC manufacturers, homeowners should replace standard air filters every 30 to 90 days.

Dirty Coils

Your air conditioner has two coils that act as heat exchangers: the indoor evaporator coil and the outdoor condenser coil. During each cooling cycle, your AC compressor routes refrigerant to the indoor air handler as an icy, low-pressure liquid. As air moves over the evaporator coil, the cold refrigerant inside it extracts the air’s humidity and heat.

This process turns cold refrigerant into a hot, high-pressure vapor gas. This gas moves to the outdoor condenser unit where it sheds its heat and condensation at the condenser coil.

Keeping your air conditioner’s coils clean ensures optimum efficiency. Buildups of dust and other debris prevent AC refrigerant from both absorbing and releasing heat. The cold refrigerant in a dirty evaporator coil will remain cold, move slowly, and eventually cause icing.

Restricted Airflow in HVAC Air Ducts

Dirty air filters aren’t the only airflow issue that can cause your AC to ice over. You might have dirty air vents, blocked HVAC air ducts, or multiple vent closures. When airflow declines in any area of your cooling system, your air conditioner works harder and may ice over or experience other problems.

Fortunately, you can clean your air vents with a soft, damp cloth. If there are heavy buildups of debris just behind these features, you can also unscrew vent covers and use your vacuum cleaner’s hose attachment to clean behind them. However, if your HVAC air ducts are riddled with debris, you may need professional air duct cleaning instead.

HVAC air vent closures inhibit airflow by causing a rise in static pressure within ducting. Closing an air vent when you no longer want conditioned air in a select area can cause problems like icing or overheating. With nowhere to go, unwanted air builds up in ducting and inhibits the flow of conditioned air to other areas. Check your home to ensure that all air vents are partially or fully open. You can also schedule air balancing service to improve airflow following AC freezing caused by vent closures.

Refrigerant Loss

If your air conditioner has a refrigerant leak, it might not have enough refrigerant to create the temperature you’ve set at your thermostat. The extra work and stress caused by progressive refrigerant loss can cause icing at the evaporator coil. In some instances, leaking refrigerant can also settle on the evaporator coil. When it does, it forms small, light-brown bubbles. HVAC technicians often call these bubbles “champagne bubbles” due to their light color and appearance.

If you spot “champagne bubbles” on your evaporator coil, turn your AC off and call One Hour for service. For safety purposes, only licensed HVAC companies should handle AC refrigerant. Running your air conditioner with a refrigerant leak could cause your AC compressor to fail.

Blower Fan Problems

Airflow throughout your cooling system is reliant upon your air conditioner’s blower fan. If this fan isn’t working properly, cold refrigerant won’t absorb the heat from warm air and will eventually cause your air conditioner to ice over.

If you can’t solve your air conditioner’s problems with freezing by changing your air filter, cleaning your air vents, and ensuring that all vents are open, contact One Hour for responsive AC service. Identifying and fixing the underlying problem early on can extend the lifespan of your cooling equipment and prevent more serious repair issues.