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Why Heating & Air Conditioning Units Stop Working In Extreme Temperatures

why do ac and heating unit stop working in extreme temperatures

Heating and air conditioning units are designed to cool the interior of a property based on the average temperature in the area. Austin, Texas, and the surrounding areas have summers with average high temperatures of about 90 degrees Fahrenheit, and winters with average low temperatures of approximately 45 degrees Fahrenheit. If temperatures greatly exceed above or below average, heating and air conditioning units have to work much harder, and in some instances, they may stop functioning altogether. 


In the state of Texas and Austin in particular, many can recall the Winter of 2021 that brought freezing temperatures that many residents have never experienced. Due to the frigid temperatures, many people experienced a loss of power. This widespread loss of power was the leading reason that Texans were without heat during the winter of 2021. But, there are several other reasons that people’s heating and air conditioning units stopped working during this uncharacteristically cold winter. In this post from our blog, Stan’s Heating, Air & Plumbing experts discuss some of the most common reasons why heating and air conditioning units stop working in extreme temperatures. 

Why Heating and Air Conditioning Units Stop Working In Cold Temperatures

Loss Of Power

Many places that do not regularly experience freezing temperatures are not prepared for such weather. Austin, Texas is the perfect example of this as we saw in Winter 2021. Austin experienced freezing temperatures estimated to occur only once every 100 years, and the damage it caused was monumental. Our infrastructure in Austin, Texas was unequipped to handle the freezing weather, resulting in an extensive loss of power.

Almost all gas heating systems in Austin still require electricity to operate. If electricity is not expected to be restored in a reasonable amount of time, precautions should be taken to prepare the home. See our blog “How to Winterize Your Heat Pump” to better prepare for potential loss of power and heat. Losing heat posts an even greater risk of pipes freezing in temperatures below 32 degrees.

Heat Pump Issues

Cold weather, snow, and ice all pose a hazard to the heat pump of your HVAC system during the winter months. Most often, heat pump issues occur during the winter as a result of debris and ice. When debris clogs your heat pump coils, the compressor may overheat and stop functioning. Debris near the heat pump can also prevent the airflow necessary to dry icy coils, leading to rust and other issues. If your HVAC system is not working but the house has power, you may want to check the condenser fan outside. If the blades aren’t moving, it could be an indication of a problem with the unit. Additionally, you should listen to the sound of the condenser engaging. Rattling and loud bangs could mean there’s a problem with the compressor motor. 

Heat Pump Issues 

Many central heating and air conditioning units in Texas use a heat pump rather than a furnace, unlike other areas of the country, such as the Northeast. Within the city of Austin, most homes and businesses use a furnace, while more rural areas use heat pumps. Simply put: heat pumps don’t play the best with excessively cold weather. Several problems can be present with the heat pump of an HVAC system, but the most common problem that can result in a unit shut down is a frozen heat pump or a heat pump that is not draining. 

HVAC systems with heat pumps often have an automatic defrost mode. This defrost mode melts the ice that forms on the coils. Frost is normal on a heat pump, but defrost cycles should remove it. If your heat pump coil has more than a quarter-inch of frost or ice, you may have a problem that needs a repair technician. If you notice that the frost does not melt and spreads to the rest of the unit, the unit is not functioning correctly.

Heat pumps may be an afterthought for most homeowners, but they shouldn’t be after what we saw in Austin this past winter. If you think your system’s heat pump is old and could require repair or replacement, reach out to Stan’s today. Also, learn more about some frequently asked questions from our customers regarding heat pumps here: Heat Pump FAQs

Why Air Conditioning Units Stop Working In Hot Temperatures

Hot weather won’t often result in an entire system shut down like cold weather can do to an air conditioning unit. During the summer months in Austin, it’s more common for AC units to struggle in “keeping up” with the hot weather. This means that they don’t cool the room to the desired temperature on the thermostat. Learn more about why AC units struggle to keep up in hot temperatures below. 

Frozen Evaporator Coil 

The idea of your AC unit freezing in hot weather may seem odd, but it’s common for evaporator coils to freeze as an air conditioner unit tries to keep up with excessively hot weather. This is especially common in the hot climates of Austin, Texas.  While simply running the air conditioner in hot weather will not cause it to freeze up, things like running the air conditioner at too low of a temperature (60 degrees or less) can cause an evaporator coil to freeze. Freon leaks, dirty air filters, and issues with the fan can also lead to a frozen evaporator coil.  If your AC unit feels excessively cold on the side of the unit where the filter is located, it’s likely frozen. It’s not uncommon for visible ice to be seen on the piping near the unit as well.  hanging off the unit as well.

For a quick fix for a frozen evaporator coil, turn off the cooling mode and turn off the fan to let the coils defrost. Make sure the filters are dust-free, as this can lead to AC units freezing as well. It’s important to not use your air conditioner in cooling mode if you think it may be frozen. This can lead to damages to the compressor, which will result in expensive repairs. Be sure to only turn the cool mode back on once you’re sure all ice has melted. Note that defrosting can take a few hours. In warm climates like Austin, it’s a good idea to head somewhere cool and comfortable while you wait for the unit to defrost. 

Low Refrigerant 

Not having enough refrigerant in your AC unit can cause it to run for excessive periods, resulting in overheating. If the home isn’t being cooled as quickly as it typically does or the unit has been struggling to match the thermostat on hot days, your AC unit may have low refrigerant. Low refrigerant is typically due to a refrigerant leak. Repairing a refrigerant leak is something best left to the professionals, so reach out to the team at Stan’s for repairs in the Austin, TX area. 

Outdoor Temperatures vs BTU Capacity 

If none of the previously mentioned potential issues is the culprit, the BTU capacity of the unit may be the reason the air conditioning unit is struggling.  BTUs, also known as British Thermal Units, are the units used to measure thermal energy. Manufacturers of air conditioning units state that when outdoor temperatures exceed 99 degrees, the total BTU capacity of the unit drops. As an example: in 99-degree weather, a 3-ton system may only be producing 2 to 2.5 tons of total BTUs. In the event this occurs, the air conditioner would not produce enough capacity to thoroughly cool the home. 

Is Your Heating And Air Conditioning Shutting Off During Winter, Or Struggling To Keep Up During Summer? Call Stan’s Heating, Air & Plumbing! 

We just scratched the surface on some of the issues that heating and air conditioning units can experience during extreme temperatures. If you find that your heating and AC system is underperforming, or shutting off entirely during excessively hot or cold temperatures, reach out to the team at Stan’s today. It can be difficult to pinpoint exactly what the problem is with a heating and air conditioning unit. The experts at Stan’s are experienced and local, so we know exactly what kind of issues homeowners in Austin, Texas commonly experience with their heating and air conditioning units. To learn more about our services or to make an appointment, give us a call or reach out to us online today.