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13 Reasons Why Your AC Blowing Hot Air?

The scorching summer heat is already unbearable and AC is blowing hot air. You’ve tried everything that you could but still no result. There has to be a good reason behind it!

After all, the worst experience one can have on a hot summer day is walking into the room to escape the heat only to find out the air vents of the AC are blowing hot air.

But the question remains, what causes your AC to blow hot air? And how can you stop it?

In this article, we will share 13 reasons why an AC blows hot air.

How Does an AC work?

A cooling agent also called “refrigerant” absorbs the heat from the inside and transfers it to the outside. This refrigerant is contained in coils known as evaporator coils.

These coils are held together in a closed system which guides the refrigerant to carry the warm air from inside the house to outside and back inside again.

Why is My AC Blowing Warm/ Hot Air?

There can be a couple of reasons behind your AC blowing hot or warm air instead of cool air that you must have been craving for.

You might need the help of an HVAC professional to resolve most of these reasons. However, you can fix a few of them by yourself at home.

Reasons for Blowing Warm Air From AC

1. Thermostat is Set Incorrectly

It may sound silly, but sometimes the problem is with the thermostat. Your air conditioner is blowing hot air maybe because there’s an issue with the thermostat. This is common with dial-type units when they are regulated incorrectly. Check the thermostat setting first.

And if you have the air conditioner manual well and good. Check whether the thermostat is calibrated incorrectly. If the issue persists, you might have to consider changing the thermostat or recalibrating it.

You can always perform some troubleshooting to see if the air conditioner is working properly. Set the controls to “auto” mode instead of “on” mode. It works for both Split AC and Wall-mounted or window-mounted AC.

If your system is set to “on” mode it will blow warm air throughout the vents when the AC is taking a break, whether or not it’s cooling the room. If you want your AC to blow cool air, switch to “auto” mode, which will actively blow cool air whenever the fans work.

Also, double-check if you have accidentally switched the thermostat setting to ‘heat’ mode. This is a mistake that is often overlooked.

2. Outdoor Unit Lost Power

If you have a split AC means you have one indoor unit which blows cool air across the room and one outdoor unit which cools down the hot air.

If you have found out that your indoor unit is blowing hot air, it could be possible that your outdoor unit has lost power and cannot cool the warm air from outside.

Typically, in this situation, there can be two cases: either you have blown a fuse, or your circuit breaker has tripped. If it has happened to you and you find out your circuit has stopped providing power to your outdoor unit, this it’s the reason behind your AC blowing hot air. It needs to be taken care of by a professional.

3. Low or Leak on Refrigerant

The refrigerant is the most important part of the AC unit that absorbs the heat from the air. Low refrigerant levels often cause the AC unit to blow hot air.

Low refrigerant levels indicate that there’s a leak in the system and that the training refrigerant is not sufficient to keep your room cool.

If this is the case, your AC will continue blowing hot air trying to reach the temperature set on the thermostat.

Refrigerant leaks can be due to corrosion and daily wear and tear. Replacing the refrigerant is not the solution to this. It’s not as simple as you thought it to be. Finding the leaks and repairing them is a time taking and expensive procedure.

If it’s not fixed properly, it can cause even more damage to the compressor which can lead to smoke coming out of the AC unit. The typical symptoms of a refrigerant leak are a hissing or bubbling noise and an accumulation of ice on the outdoor unit.

4. Evaporator Coils are Dirty/ Frozen

Evaporative coils are located in the indoor unit, which plays a major role in cooling the air. Filled with refrigerant, these coils act as heat absorbents. However, these coils can become dirty and clogged, restricting their ability to cool the air effectively. If that’s the case, the AC won’t be able to cool down the room and will continue blowing hot air.

Sometimes, these evaporative coils become frozen, leading to blowing hot air. When the evaporator coils don’t get proper airflow, they become frozen, resulting in the buildup. If this is the case, then your unit will release hot air or sometimes no air at all. Warm air must flow around the coils for them to function effectively.

5. Clogged Air Filters

Air conditioners have these air filters which trap all sorts of dust, debris and pathogens keeping your room clean and the air safe to breathe. Over time, these air filters become saturated and need to be cleaned.

Clogged air filters block the cool air from circulating across the room. It can make your unit overwork which puts pressure on the compressor and can lead to other AC problems.

So you should clean your air filters every 30 to 90 days. The frequency of changing your filters depends on a few factors, the presence of pets, allergy sufferers, the number of smokers, and the workload of your air conditioner.

6. Malfunctioning Electrical System

The most common reason is car AC units. The AC in your car is electrically powered, and if it’s blowing hot air, there’s a high chance of electrical malfunctioning.

The entire electrical system will shut down if even one of the parts in the arrangement of fuses, relays, and switches ceases to function as it should. Electrical systems can be complex to understand, so it’s always better to fix them by a car mechanic.

7. Clogged Condensate Line

Condensation is produced in large amounts throughout your air conditioner’s heating and cooling cycle. This moisture is transported outside via the condensate line, usually from an exterior wall of your house, where it empties.

The atmosphere around the drain line is continually moist, so it’s common for buildup, including mould or algae. When the line is blocked, your AC system cannot effectively remove humid air, resulting in heated air circulating throughout your home.

8. Malfunctioning Compressor

When you turn the AC on, the refrigerant in your AC system is cycled through the unit and blows cool air. If you have a faulty compressor unit, the refrigerant cannot turn from gas to liquid and cannot cool the air. The refrigerant should turn into liquid to blow cool air, and a malfunctioning compressor often blocks the process.

9. Duct Leaks

There can be a leak in your home duct, causing the AC to blow hot air. The ducts in your home system carry out the cool air, and sometimes a leak in the system can allow the warm air to mix with the chilly air, which may blow a warmer air than usual through your vents. A specialist should always handle problems with ductwork. To prevent any of these problems from occurring, service and clean your ductwork system every 3 to 5 years.

10. Fan Problems

The fans in your air conditioner may not be working correctly for a number of reasons. It might be due to a faulty motor, worn belts or inadequate lubrication. Accumulation of dirt and debris may also cause the malfunction of the fans.

If the fans, whether indoor or outdoor, fail to blow air as they should, it would lead to poor airflow. This then causes the AC to blow warm air instead of cool air, as you expect.  If left unattended, fan issues could lead to compressor failure. You could occasionally notice the AC button flashing.

11. Breaker Switch

There are AC systems that comprise an indoor unit and an outdoor unit. If your indoor unit is doing fine, but the outdoor unit has lost power, it can cause the unit to blow hot air. If you see a tripped breaker, turn the switch to the “on” position and let the AC run for a couple of minutes. If the breaker trips again, you need to get it fixed by a professional.

12. Return Vents are Blocked

Many people shut the AC’s return air vents during winter and reopen them in the summer. Make sure you reopen the return vents for the vents to work correctly. Double-check that no furniture or objects are blocking the AC return air vents.

13. Time to Replace AC Unit

Sometimes, the issue is simply that your air conditioner can’t do its job as it did before. If the AC has been providing service for 15 years or more, and you are experiencing problems regarding its performance, maybe it’s to retire the old unit.

Final Words

There can be several reasons behind your AC blowing hot air. If your AC blows hot air, it’s because of the above reasons. You need to do basic things to maintain your AC for longer, like replacing the air filter once every 3 to 9 months, depending on your use, scheduling routine servicing once a year and trying to keep the temperature constant

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