Why is My Air Conditioner Frozen?

Why is My Air Conditioner Frozen?

It seems to happen every summer — one minute you’ve got a cool, air-conditioned home. Next minute, vents are pumping out warm air. One look at your HVAC system provides the diagnosis: a sheet of ice covers the evaporator coils. You must wonder, “Why is my air conditioner frozen?”

How to Unfreeze Your Air Conditioner

Your AC may freeze up for several reasons, but first, you need to defrost it.

The first thing you’ll need to do is turn off your air conditioning.

Continuing to run it while frozen can burn out the compressor. If you’ve ever had to replace an AC compressor, you know what an expensive process it is. Some experts recommend turning off the power at the breaker.

Next, you’ll have to wait. It may take 24 hours to defrost completely.

Make sure the condensate drain pan is draining properly. As it melts, the frozen water on the coils needs to be removed. You don’t want water damage to add insult to injury.

Turn on the blower with the AC switched off to expediate the process. If you turned off the breaker, use a regular box fan or tower fan to circulate the warm air from your home over the frozen coils.

Resist the urge to remove the ice by hand. It can further damage your system, especially if you try to chip it off with a tool.

Once the coils have defrosted, use a shop vac to clean up any puddles and let the blower fan complete the job of drying out your air handler closet.

Make sure the coils are completely dry before turning the air conditioning function back on.

Other Steps to Take

While you’re waiting for your coils to defrost, some additional investigation may reveal why your air conditioner is frozen.

Check filters

Dirty filters are the most common cause of a frozen air conditioner. Trapped dirt in the filter impedes consistent airflow, and this causes your AC to work harder.

At a minimum, check your filter every three months. If you have pets or kids, check it monthly. HEPA or allergy-reducing filters can clog sooner than more traditional filters.

Check the evaporator coils

Now that they’re not covered in ice, check the coils on your evaporator to see if they’re dirty. A build up of residue (often caused by that dirty air filter) can cause them to freeze up.

You can clean the coils using a commercial spray for that purpose, although many find mild detergent to be adequate.

Check the vents

If your intake or vents are blocked, it can restrike the airflow through your home. This can also cause your AC unit to freeze up.

Make sure all of the vents are fully open and remove any obstruction from the intake grille that serves the air handler.

Some homes are designed for air to flow through undercuts in doors. You may see gaps under the doors to bedrooms or bathrooms. Make sure there’s nothing blocking these gaps, such as rugs or the family dog.

Why Your Air Conditioner Froze

As stated above, the most common reason is obstructed air flow from a dirty air filter. But it isn’t the only reason.

Low coolant levels

Low coolant levels also cause freezing. Low levels of refrigerant reduces the pressure inside the unit. The temperature then drops in the coils, even below freezing, which can cause them to freeze up.

Frost accumulates on the coils, and this builds up as the unit struggles to operate. Eventually, you’ll find a sheet of ice on your evaporator coils.

You can purchase a coolant kit, but your best choice is to call a professional technician. Low levels of refrigerant usually indicates a leak somewhere in the system. A professional can locate and repair the leak efficiently and safely.

Faulty blower fan

The blower fan circulates air over the evaporator coils, removing cold air and circulating it through the ductwork. However, if the blower isn’t running properly, the evaporator can freeze over.

You may notice the lack of cold air coming from the vents long before this occurs, but it’s worth checking. Worn belts and bearings can interfere with efficient operation.

Problems with the electrical wiring to the blower fan can also cause it to operate at inadequate speeds.

Check the vents for airflow and the blower fan for strange (or no) noises during operation.

In either case, you should call an HVAC technician to service the blower fan.

Don’t spend another day defrosting your AC and hoping it rallies to the cause. Make an appointment today with the experts at One Hour Heating & Air Conditioning in Chattanooga. We’ll pinpoint the cause of your frozen AC unit and make sure you don’t spend another hot day waiting for it to melt.