Why Does My Air Conditioner Freeze Up?

Why Does My Air Conditioner Freeze Up?

When we see ice or frost on something we automatically think “cold”, so this must be good thing for an air conditioner, right? Wrong! If your air conditioner is freezing up, or you see frost or ice on parts of your AC Unit, there is a problem and you need to call someone for air conditioner repair.

So why does an air conditioner freeze up in the first place? There are a few reasons you may find ice forming on your air con unit, and in many cases, it’s a combination of a few problems that eventually lead to a frozen evaporator coil and refrigerant plumbing lines. The most common reasons for an air conditioner freeze up are:

  • Your AC Unit Is Low on Refrigerant (Freon): When an air conditioner develops a leak in the refrigeration system, it becomes undercharged. The evaporator coil or “indoor coil” will collect moisture from the air which will quickly freeze on the cold coil. If the unit is allowed to keep running more moisture builds and more ice forms.

Tip! To read more articles related to refrigerant, and leaks, visit our Blog page and search the term “Freon” in the search tool in the right hand column.

  • Restricted or Lack of Airflow: When there is insufficient air moving across an air conditioners evaporator, the moisture buildup described above will cause the coil to freeze. Things that cause a lack of airflow across a coil are; a dirty air filter, a non-functioning or “slow” indoor blower fan motor, restricted or undersized air ducts, or long-term dirt buildup on the coil – usually due to infrequent filter changes or using cheap air filters.
Phoenix ac maintenance

Dirty vs. clean air conditioner coil

  • Malfunctioning Metering Device: If your ac unit is less than 15 years old, it probably has a metering device known as a TXV (Thermostatic Expansion Valve). Think of a TXV as a traffic light for refrigerant – it controls the flow of refrigerant through the system. A malfunctioning or “sticky” metering device can cause frost to build up on components of your HVAC system.
  • Ambient Temperature Too Low: While most modern air conditioners are equipped with sensors that can automatically shut-off the compressor if the outdoor air temperature is too low (below about 60 degrees Fahrenheit), not all do, or the sensors themselves can malfunction. Running you’re A/C when it’s too cold outside can cause a freeze-up.
  • A Combination of Problems: When an air conditioner is slightly undercharged (low on refrigerant aka “Freon”), say 1 or 2 pounds’ low, you may not even notice at first. Combine that undercharge with a slightly restricted air filter or a sometimes sticking TXV and both problems happening together may be enough to cause ice buildup and in short time a completely frozen air conditioner coil.

Frozen Air Conditioner Condenser Coils


 What Should I Do When My Air Conditioner Is Already Frozen Up?

Now that you know why your AC unit is freezing up, here’s what you should do:

  1. Turn Your AC Unit Off Immediately: It’s not going to get better or fix itself so the first thing you should do is turn your air conditioner thermostat to the OFF position. Turning your thermostat off will not only allow the ice to thaw, it will prevent damage to other components – specifically the AC compressor.
  1. Check/Replace Your Air Filter: A very clogged air filter can cause your air conditioner to freeze up. Check your filter. Is it very dirty?

If YES – After your unit is completely thawed out (NOTE: This may take several hours or even a whole day), put in a new air filter and try turning the unit back on, and go to step number three.

If NO – Unless you were in fact running the air conditioner when the outdoor air temperature was below 60 degrees Fahrenheit as we discussed above, it’s time to call a licensed air conditioning company to diagnose which of the above problems caused the ice-up.

  1. Check Your Airflow – Is It Blowing as Hard as Usual?

If YES – Most likely the dirty filter was the cause of the problem. Keep an eye on the equipment for a few hours / days and make sure no more ice appears. If no ice appears, congratulations your problem is most likely fixed – change your filters more often! If ice does appear, turn the unit back off and call for repair.

If NO – You have another problem and need to call an AC Contractor for further diagnosis and repair.

  1. Schedule an Air Conditioner Repair or Tune-Up: If you’re problem was solved by following the steps above, great! We’re glad we could help! But don’t forget to have a licensed HVAC Company inspect and tune-up your AC unit at least once per year. Air conditioning equipment manufacturers have found that customers who schedule periodic maintenance have lower failure rates and warranty claims than those who do not.

If you’re evaporator coil or other components are still freezing up, it’s time to schedule a repair.

Magic Touch Mechanical is located in Mesa, AZ and provides air conditioner repair and replacement services throughout the Phoenix-Metropolitan Area and surrounding neighborhoods. To check to see if we service your area, enter your zip code here.

If you are outside of our service area, there are plenty of highly rated and trustworthy service companies throughout the USA and Canada. Read on for some tips on how to choose wisely.

Choosing the right HVAC (Heating, Ventilation, and Air Conditioning) Contractor is no different than choosing the right family doctor. You shouldn’t just call the first name that pops up in the search results. For more information about choosing the right AC Company check out these articles:

Don’t choose the first air conditioning company that shows up in the search results.

Tips for hiring the right contractor for the job.

If your air conditioning and heating system requires extensive repairs, uses the older R-22 refrigerant aka Freon, or is more than ten years old; you may want to ask your service technician about doing a repair vs. replace comparison with you. A good company will “advise” you, not “sell” you, and allow you to weigh out the options to determine what’s best for your family and budget.

To schedule service with a Magic Touch Air Conditioning Technician today, call (480) 855-8789 and one of our friendly Customer Service Representatives will be happy to assist!