Your central AC unit cools your home by pulling in warm air
and blowing it over refrigerant-cooled coils to remove the heat and cool the
air. Then it recirculates the air throughout your home.
Sometimes, though, something goes wrong with the airflow or
cooling cycle and your AC stops blowing cold air and instead ices over. When
this occurs, you may see actual ice forming on the outside unit. The following
can help you determine the cause.
1.
Reduced Air
Flow
Insufficient airflow through the AC unit results in cool air
not being moved away from the condensing coils quickly enough, which can cause
the unit to freeze up in the pooled cold air.
Cause
The most common cause of poor
airflow is either a dirty air filter or the wrong air filter. Some high
efficiency air filters have small pores that won't allow sufficient airflow
through the filter, which means they perform as though they are dirty and
clogged even though they aren't.
Another issue that can occur is blocked air return vents. If
an air return is blocked, your unit won't be able to pull in enough air to
properly move cold air from the coils.
Repair Options
Begin by checking your air filter. If it appears dirty or
discolored, then it is time to change it. Next, verify the maximum filter
efficiency rating for your AC unit with the manufacturer's specifications. Only
use a filter that falls within this recommended range.
To finish your airflow troubleshooting, check all the return
vents throughout your home and verify that they are open and not blocked by
furniture or other items.
2.
Low
Refrigerant
A lack of refrigerant in the AC system makes it impossible
for the coils to absorb the heat from the air blowing over them, so instead the
coils will freeze up.
Cause
The refrigerant in your AC unit is in a closed system, so if
you have low refrigerant, the refrigerant lines probably have a leak. The first
signs of a leak are poor cooling, increased energy costs, and hissing sounds
from the lines in the unit. As the refrigerant levels drop, freezing and a
total lack of cold air will occur.
Repair Options
A refrigerant leak is a two-part repair that an HVAC
technician must complete. The first part involves locating the leak or leaks,
which can take some time. Once the technician finds the leaks, they will repair
them and recharge the system with new refrigerant.
If you suspect a leak, call in a tech immediately. Exposure
to refrigerant can pose a health risk, so it's important to have the problem
quickly addressed.
3. Fan Mechanical Issues
The fan or blower in your AC unit is what moves the air
through and blows it over the coils. If the fan malfunctions, then insufficient
air blows over the coils and they freeze.
Cause
Several mechanical issues can lead to a poorly functioning
fan. Sometimes the issues are electrical, such as a blow capacitor. In other
instances, the issue is with the fan itself. It may be out of balance, jammed
with dirt, or the bearings or fan belt may need replaced. Damage to the fan,
such as a bent blade, can also lead to poor function. Another issue that can
affect the fan is a broken motor.
Repair Options
Bring in an HVAC tech if you suspect that the fan is the
root of the problem. A full inspection and tune-up may be necessary to find the
exact mechanical issue leading to improper operation. In most cases, the tech
can repair the problem by replacing the malfunctioning electrical component,
cleaning and rebalancing the fan, or repairing the motor. In some cases,
though, you may need to have the fan assembly replaced. Contact A-1 Finchum Heating & Cooling for more
help.
