Turning the HVAC fan to ON will force it to blow warm air over any frozen coils—which will speed up the defrost process. Make sure it's actually set to ON and not to AUTO. Automatic settings cause the fan to cycle—starting and stopping over and over again.
If you can't see any mechanical or cleaning issues, contact an HVAC professional. Broken thermostat: A faulty or broken thermostat is a common cause of a frozen AC.
First Things First: Ice Is Not Always a Bad Sign
Moisture in the air condenses on your unit, then freezes in the cold air. Your HVAC unit is designed to deal with ice by running a periodic defrost cycle, heating the outside of the unit and melting any snow or ice that's accumulated on it.
Disconnect the thermostat and put it in a cup of ice water with the wires coming out. Only dip the sealed portion of it to avoid an excess of water getting inside the thermostat. Wait a few minutes for the thermostat to get cold. Now check for connectivity between the wires.
In the past, when my coil froze, I ran the heater briefly 2–3 minutes, followed by the fan to melt everything. Seems to work great for me.
Air conditioners are designed to function in a specific temperature range. If you are running your air conditioner when the outside air is below 62 degrees, then the pressure inside your system will drop, and this can cause your air conditioner to freeze up.
You should also have dirty evaporator coils cleaned or replaced to prevent ice. Change Air Filters Regularly: Replace air filters every 1-3 months to maintain proper airflow. Clean Coils: Schedule annual maintenance to have evaporator coils inspected and cleaned.
First, check your filters and coils for dirt and debris that may be impeding airflow. Once you've cleaned the filters and coils, run the air conditioner with just the fan so that the ice accumulation can melt off. If the AC still doesn't blow cold air, it could be that refrigerant levels are too low.
Make every effort not to use your ac unit when it's frozen, as this could unduly strain the compressor. Note: The compressor is the most expensive component of your AC. Excessive strain could damage this valuable component leading to a costly repair service call or replacement.
Signs You Have a Frozen Evaporator Coil
Ice accumulation is visible around the evaporator coil. The temperature displayed on the thermostat does not match the actual indoor temperature. Frozen lines and ice buildup near the outdoor unit are observed. Water leakage or flooding near the drain pan.
If the thermostat malfunctions and detects the wrong temperature, this can cause your A/C to run too hard for long periods of time. If your A/C runs for too long it can cause the coils to freeze.
Dirty air filter: A dirty air filter can restrict airflow, which can make it harder for your AC unit to cool your home. If your air filter is dirty, it's recommended to replace it every 1-3 months. Low refrigerant: Refrigerant is a liquid that helps your AC unit transfer heat from inside your home to the outside.
Since 72 degrees is generally agreed upon to be an ideal indoor temperature, most people would probably still feel comfortable setting their AC units slightly higher than this, perhaps at around 75.
If your AC is running but not cooling, it could be due to a dirty air filter, incorrect thermostat settings, a malfunctioning thermostat, a refrigerant leak, dirty condenser coils, blocked vents or ducts, a faulty compressor, frozen evaporator coils, or electrical issues.
Leaking or Low Refrigerant
The most likely cause of this is a leak. A leak not only keeps the AC unit from cooling properly, but also it can cause other issues within the home. For example, when it isn't cool enough, humidity levels can rise in your home making it feel hotter than it is inside.
Air Filter Check
A dirty air filter can sometimes be the culprit of an AC freezing over and leading to frigid air blowing throughout your home. Dirty air filters create impedances in airflow that can make your AC work harder than it needs to, and you are burning the candles on both ends of your HVAC.
Generally, it will take about 24 hours for a frozen air conditioner to thaw out completely. Regardless of what caused the unit to freeze, the key to getting it thawed out is to turn off the system and let it sit for a while.
Once the AC unit has thawed completely, and you've done a check on the filters and the air registers. It is now time to fire the system on. Switch ON the thermostat and set it at COOL. If the AC is working correctly, the air registers should blow cold air into the room.
When the filter becomes dirty, this can block airflow and cause the evaporator coil to get too cold, which can lead to a frozen AC unit. As a general rule of thumb, many HVAC professionals recommend replacing the air filter every 90 days.