Learn what to look for when your air conditioner isn't cooling and detect the signs reflecting an overworked unit.

Who enjoys sweltering in the summer heat? If you want to ensure that your air conditioner continues to blow cool air in the depth of the summer months, read on for eight reasons your AC is not cooling and how to get it working properly again.

Why is My AC Not Working?

1. Is There Power? - If the electricity to your home seems fine, but your air conditioner is not turning on, check the breaker. If it's been tripped, your fix may be as easy as flipping that switch.
2. Improper Settings are on Your Thermostat - You can help your air conditioning unit work efficiently by keeping the thermostat set at a steady temperature. For the best efficiency, you should set the dial to a temperature that feels comfortable, but not too cold. The Department of Energy suggests that having a fan on and setting the temperature at 78 degrees is the perfect energy-saving method. Otherwise, the AC unit would have to kick on and off repeatedly all day to keep the temperatures low.

3. Dirty or Wrong Size Air Filter - If you're question is "Why is my air conditioner running but not cooling the house?", this may be your answer. As the AC filter clogs with dirt and debris, the efficiency of the system plummets, causing you to pay extra money for less cooling power. In addition, the air conditioner blower must work even harder than normal, which can lead to internal damage. For best results, change your filter every one to three months on average but check it monthly during times with high pollen counts or excessive dust. If you are still unsure how frequently you should be changing your filter, we've got you covered with additional advice.

   How often you replace your filter isn't the only possible reason your air conditioner is not blowing cold air but is running. The wrong air filter size can cause your AC unit to be overworked as well. Always check the make and model of the unit and purchase the correct filter size accordingly. If your old filter does not have labels with the size, grab a tape measure or ruler and take a look at our guidelines on “How to Measure Your Air Filter”.

4. Faulty Switch - Your air conditioner operates best when the blower can constantly push cooled air through the ducts. Otherwise, the chilled air remains in the system, causing the internal components to freeze and stop working. The most common causes of weak airflow are a clogged air filter or faulty fan switch. If a filter change does not instantly fix the problem, you may need additional diagnostic tests performed by a licensed HVAC professional.
5. Clogged Drain Lines - Over time, the drain lines in air conditioners get clogged with debris. Once the drain lines are clogged, the air conditioner cannot adequately remove moisture from the air to cool it to optimal temperatures, resulting in your home central air conditioner not blowing cold air. As part of your seasonal cleaning, try to clear out the drain lines to keep your AC unit efficiently producing cool air. If you are unsure of the location of your drain line, set up a HVAC consultation. An expert may be able to show the location of your drain line.
6. Closed Vent Flaps - The AC unit utilizes exterior vent flaps to release warm air and moisture left over from the cooling process. When the vent flaps are turned to the closed position, the warm air remains in the case and kicks the system into overdrive. When this happens, you may notice that the air coming out of your interior vents feels warmer than usual.
7. Wrong Unit Size - When you purchase a new air conditioner, it is necessary to match its size to the square footage of your home to avoid overworking the system. An improperly sized air conditioner will work too hard and too long as it attempts to cool the space. This will cause it to develop premature wear and damage that often leads to the failure of internal parts.
8. Un-insulated Ducts - If your air conditioner ducts are not properly insulated, the cooled air may rise in temperature before it enters the room. Since wildlife like squirrels and raccoons can remove this material from the ducts, be sure to double check the insulation on a regular basis to avoid accidentally overworking the cooling system.

Why Is My AC Blowing Warm Air Instead Of Cool Air?

During the hottest weather conditions and especially during summer months, you should routinely change your air filter to prevent problems from developing. There can be various reasons it blows warm air. If your AC is blowing warm air, inspect your air filter, check your thermostat, review your circuit breaker, and enlist the help of a professional technician who can assess your system for leaks. Regular maintenance can prevent further damage and restore cool air to your home.

What Causes An Air Conditioner To Stop Cooling Altogether?

A leak could indicate a low refrigerant level that keeps your AC system from working properly. A dirty air filter could make your entire system overheat. Your thermostat settings might not be set correctly. Tripped circuit breakers or a faulty compressor could also be to blame, disrupting the cooling process. 

If your AC filter is clogged with dirt and debris, it reduces the efficiency of your HVAC system, and it costs more to run. The system’s blower then has to work harder.  This can also cause your system to shut down altogether.  Using the wrong filter size can cause problems with your unit as well. If you change your AC filter regularly and use the correct size, your system is more likely to operate properly. Always check that the filter you’re using is the proper size. A faulty fan switch could also cause your weak flow. Have your AC unit checked if you think this might be an issue. Additionally, if your vent flaps are closed, warm air could overwork your unit and cause it to overheat. 

Consult our handy guide “How to Measure Your Air Filter”, if you don‘t know how to measure your air filter. Routine maintenance, like cleaning filters and checking thermostat settings, can frequently resolve minor issues, but you may need professional servicing for refrigerant or mechanical problems. 

Why Does My AC Struggle To Cool On Very Hot Days?

When temperatures rise your AC unit might have difficulty keeping up. Your system will work harder to maintain a cooler indoor temperature, because its heat load increases. If your AC unit is smaller than it needs to be for the size of your home, It may not be able to cool properly when extreme heat occurs. 

It's also harder for it to operate if your home has poor insulation or air leaks. Dirty coils, air filters, or low refrigerant levels can also cause low performance. Seal any leaks to improve operation during high temperatures and make sure you routinely change your air filter. You could also consider upgrading to a more energy-efficient unit if yours isn’t sufficient for your home. 

Could A Dirty Evaporator Coil Be Why My AC Isn’t Cooling?

It's possible a dirty evaporator coil could be why your AC isn't cooling the air in your home or business. The evaporator coil absorbs heat but if it's covered in dirt or debris, it won’t work properly. The buildup of dirt and debris surrounds the coil and causes your system to blow warm air, instead of cool air. Dirty coils reduce the airflow, overwork your system, and can cause your system to freeze up. You might need to have the coil cleaned to prevent system strain and ensure it works correctly.

Can A Low Refrigerant Level Cause My AC To Stop Cooling?

Refrigerant absorbs heat from indoor air and releases it outside, which is how the system cools your home. When your refrigerant level is too low, or has a leak,  it can lead to warm air blowing from your vents. If the level is low, the evaporator can freeze up. A professional technician can locate leaks and recharge your system so it cools properly. 

Why Does My AC Turn On But Not Cool The House?

If your AC turns on but isn’t cooling your house, some reasons may include a dirty air filter, a clogged evaporator coil, low refrigerant levels, problems with your thermostat, or a malfunctioning compressor.  The first thing to determine is if your air filter is dirty and needs to be changed. 

Why Is My Air Conditioner Leaking Water And Not Cooling?

An air conditioner that leaks water and doesn’t cool can be due to various problems. A clogged condensate drain line can cause water to back up and leak. A dirty or frozen coil can cause excess condensation and prevent cooling. Low refrigerant levels, which cause the coil to freeze and then melt, can also cause water leaks and reduce cooling. Dirty air filters can limit airflow, causing the system to overwork. Have your AC system maintained and checked regularly to avoid these problems.

Why Does My AC Make Strange Noises And Fail To Cool Effectively?

Strange noises coming from your AC unit, combined with poor cooling, could mean it has mechanical or airflow issues. Mechanical issues reduce your system’s efficiency, preventing it from cooling. Buzzing or humming sounds might be evidence of electrical problems, like a failing capacitor or faulty motor. Grinding or squealing noises can be from worn-out components like bearings or belts. Rattling or banging could mean loose or damaged parts inside the unit. Check that your air filter isn’t clogged and that your coils aren’t dirty. An HVAC professional can diagnose more complex issues and restore your unit to full functionality. 

Can Thermostat Issues Cause My AC To Stop Cooling?

Thermostat issues can cause your AC to stop cooling. If your thermostat isn’t set correctly, your AC unit won’t work properly. Faulty wiring, dead batteries, or improper calibration can cause your thermostat to malfunction. First, change the batteries. Troubleshooting possible malfunctions sometimes resolves these problems.

Why Does My AC Trip The Breaker And Stop Cooling?

Your AC unit might trip the breaker and stop cooling due to electrical or mechanical issues. A dirty air filter or clogged condenser coil can restrict airflow, draw more power, and cause your system to overheat. Your compressor can be strained by a low refrigerant level and lead to overheating, then tripping the breaker.  A faulty capacitor, motor, or damaged electrical parts could cause power surges. If the breaker is old, worn out, or undersized, it can also be tripped. Don’t reset the breaker repeatedly, because it could damage your AC unit or electrical system. Call a professional instead to evaluate the problem. 

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