Like broken fans, dirty filters can prevent air from flowing adequately throughout the system. If air doesn't circulate properly, the coils in the A/C unit can get too cold, and end up freezing. Dirty filters can also contribute to extra wear on your compressor, lowering the life expectancy of your A/C unit.
Dirt will make your AC less efficient, which means you'll have higher energy bills each month. Dirt buildup on your AC coils will make it difficult for the system to absorb and dump heat, causing the system to be less efficient. You may even start to feel like your AC is running constantly.
Usually the cause of the coil freezing up is reduced air flow though the coil, caused by things such as dirty air filter or something blocking the air coming into the unit. Also, low refrigerant level can cause it.
Signs that your AC coils need cleaning include reduced cooling efficiency, longer cooling times, and higher energy bills. If you notice these issues, it's time to clean the coils.
1st Step: Turn Your HVAC Unit Off.
Even if it's sweltering outside, you still need to turn OFF your air conditioner! Running a frozen air conditioner will wear out parts much faster, and could overheat your unit. Worn parts are bad news for the most expensive piece of your HVAC unit—the compressor.
Brush Off Loose Debris: Using a soft brush or a specialized furnace coil brush, gently brush away any loose dirt or debris from the coils. Be gentle to avoid bending the fins or damaging the coils. Vacuum the Coils: Attach a soft brush to your vacuum cleaner and carefully vacuum the coils.
AC Coil Cleaner Method: Compressed Air
Cleaning the indoor evaporator coil with compressed air will blow dust and debris inside the home. Using compressed air can be a quick and reasonably effective method to remove surface dust, dirt and debris from the coil.
An issue with the thermostat can cause your AC to run longer or more frequently. If the AC coils are freezing, the unit may be working more than it needs to. Have the system checked by a professional if your home is too cold or the indoor temperature fluctuates.
How Often Do I Need to Change Out My Air Filter? Generally, most air filter manufacturers and HVAC companies recommend changing your air filter every 90 days, or 3 months. That can change based on where your home is located (ex. dusty, dry climates), if you have any pets, and the age of your system and equipment.
Most HVAC professionals recommend AC coil cleaning once or twice a year. If dust and dirt build up on the coils, major problems can occur. The AC coil cleaning cost is around $100 to $400 as of 2024, according to Homeguide (for an evaporator coil), and up to $700 to remove and clean the coil.
After cleaning the coils, wait 30 to 60 minutes before turning on the air conditioner.
How Long Does An AC Coil Last? The lifespan of your system's coils isn't set in stone, but factors such as the quality of the coils, the frequency of use and the level of maintenance they receive are all relevant. On average, evaporator coils can last anywhere from 10 to 15 years.
Turn the Thermostat Fan Setting to On. Turn your thermostat fan setting to “On” so that the fan continues to blow air over the coil. The warm air in the home will naturally defrost the frozen coil. In severe cases, the heat can be turned on to speed up the process.
An extremely dirty evaporator coil can cause your AC to breakdown completely. This happens when condensation forms on the dirt and then freezes during the AC's operation. The buildup of frost stops the heat transfer with the air in your home, which causes the air conditioner to stop cooling air at all.
Ice on your HVAC unit wastes energy, and it can cause damage or failure. If you have ice on your outdoor unit, turn your system off, check for problems, and contact a professional to repair any damage.
In most cases, you can get away with cleaning your coils once a year with a seasonal tune-up. However, you should consider where your unit is located. If you're in a big city with heavy air pollution, you may want to have the coils cleaned two times a year.
Refrigerant leaks are a common cause of frozen coils. Refrigerant is the chemical that runs through your AC coil, changing pressure and temperature in order to absorb heat. If it leaks, the lack of pressure will make it absorb more heat than it should. This makes the refrigerant lines, and then the coils, freeze over.
While Dawn dish soap is a versatile cleaning agent, it's not recommended for cleaning AC coils due to its chemical composition. Household cleaners like Dawn may not effectively remove stubborn buildup and could potentially harm the coils or other components of the system.
You could also use a homemade mix of water and mild detergent (like dish soap) instead of commercial chemical cleaners. After cleaning the coils, it's also a good time to inspect the other parts of the unit. Inspect the condensate drain pan and remove anything that doesn't belong there.
Homeowner: A new evaporator coil replacement costs $630 to $1,700 if it is still under warranty. Homeowner: An indoor AC coil replacement costs $1,230 to $3,700 if it is no longer under warranty.