Frozen Air Conditioner

Your refrigerant temperatures are dropping because of something in the system that is causing your AC to freeze up. The condenser coil and/or evaporator coil may freeze as a result of this. If you put your hand in front of your supply vents and you sense warm air coming out, you probably have ice somewhere in the system. You may also notice a hissing sound coming from the unit.

Although it may seem counter-intuitive for a system that’s used in the hottest weather to freeze, it can and does happen to many unprepared homeowners every year.  A frozen air conditioner can leave you and your household in an uncomfortable situation on a hot day. With frozen coils, there’s going to be ice or frost on the coils and possibly pipes of your indoor unit. However, many indoor units aren’t accessible, so you might not be able to see that. The first symptom of any HVAC problem you are likely to notice is the heat. If your AC doesn’t feel like it’s working as it should, there are a few things you can inspect to get more info on the problem.

Why AC Unit Coil Frozen Up

The root cause for your AC freezing up is usually the manipulation of the Joule-Thomson Effect, which is the principle of thermodynamics that allowed us to create an air conditioning unit in the first place. Stick with us, we won’t get too technical here.

The Joule-Thompson Effect

The Joule-Thomson Effect is a theory that describes how the flow of gas and pressure work together. In short, the method says that if gas expands, then pressure and temperature will decrease as a result and vice versa. This is important because your air conditioner works by the evaporator coil expanding refrigerant the liquid agents that make your AC work to absorb heat in your home, and then pushing cool air out as a result. So, your air conditioning unit expands refrigerant and decreases the temperature, sometimes causing it to malfunction, and a frozen AC unit is the result.

You must turn off the system if your air conditioner has frozen because of filthy air filters. Airflow obstruction is likely the basic reason for this problem. Allow your air conditioner time to thaw, leave it off for a few hours. Once the system is deactivated, we recommend operating the fan for an hour. While the fan runs, change your air filter according to the directions of your unit model. There are also a few different AC problems that can cause your refrigerant temperatures to drop and freeze up the system.

  1. Lack of airflow
  2. Clogged air filter
  3. A dirty evaporator coil
  4. Obstructed air vents
  5. A refrigerant leak
  6. Faulty blower motor
  7. The outdoor temperature is too low
  • Lack of airflow

The evaporator coils work by absorbing heat from the air. But if they don’t have enough heat to absorb, the condensation on the coils can freeze. Low airflow can be caused by dozens of problems within the AC system, such as a malfunctioning blower fan, dirty air filters, or even damaged ductwork.

  • Clogged air filter

If your air filter is clogged, it restricts air from passing over your evaporator coil (part of the inside unit). If warm, unconditioned air doesn’t pass over the coil, the temperature of the refrigerant inside the system drops and can freeze over. Start by replacing the clogged air filter with a new one. Then, turn off your system and allow it time to thaw out. Once it is thawed, run the system as usual. If there are additional problems, contact a professional to evaluate your AC system.

  • A dirty evaporator coil

If dust and dirt build up around the evaporator coils, which transfer refrigerant to the heat pump, it will put extra strain on your system to condition the air, putting your evaporator coil at risk of freezing. The coils need to be cleaned periodically for proper heat absorption to occur; otherwise, the coils may just freeze over.

Have a professional clean your indoor coil. This repair shouldn’t be attempted by a homeowner as your evaporator coil is located inside your air handler and contains refrigerant, a gas that can be harmful to humans.

  • Air vents issue

Your AC air ducts are vital for a properly working system. However, they can experience problems at any time. From leaks to blockages, these air duct problems can result in very poor airflow. If furniture, curtains, or other objects are obstructing the air vents in your home this prevents air from being passed through the system. Restricted airflow can cause the coil to ice over.

 If you notice your AC freezing up, including weak airflow coming from your vents, schedule a duct inspection appointment with a professional.

  • Low Refregraton Levels

If you notice your AC freezing up, your system could be low on refrigerant. This substance is a cooling liquid that cools the air before it enters your home. But for this substance to work effectively, your system needs enough of it. The outdoor unit, called the compressor, uses this refrigerant to pump cool air into your home. When there isn’t an adequate amount of refrigerant in an AC system, the pressure will drop inside the unit. This will then cause temperatures to fall in the evaporator coils which can dip below freezing. When this happens, nearby water vapor can grab onto these coils and freeze. This is one of the leading culprits of an AC freezing up. After the initial coat of frost accumulates on the coils, it can eventually build up to a thick sheet of ice.

  • Faulty blower motor

The blower motor and fan help to blow air over the coils in the system, which helps to create cool air. When this fan stops working, cool air won’t be coming from your vents. This can cause a frozen AC unit. If you’re not sure what to do when your AC unit freezes up, inspect the blower motor and fan. If this is the problem, you may hear rattling sounds coming from your air conditioner.

  • Temperature


When it’s cold outside, the heat pump and air handler will not function very well, causing the evaporator coil to freeze. A faulty thermostat is one of the possible reasons for inside and outside temperature variation.

Diagnose your thermostat regularly. Always put your thermostat recommended setting while away from home. Avoid setting your thermostat too low as it can cause the Ac unit to freeze up, especially when it isn’t that hot out.

Contact Us

We are licensed and approved technicians and available around the clock. We can fix any problem regarding Ducts Cleaning which is making you annoyed. Ducts Cleaning is locally owned and well recognize around Melbourne.

Give us a call on 0404 667 916 or contact us and get your service’s cost before we arrive for the job.

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