Air Conditioner Running But Not Lowering Temperature?

Air Conditioner Running But Not Lowering Temperature

Hot weather is a lot more tolerable when you have air conditioning to escape it. It can be frustrating when your air conditioner isn’t cooling your home.

There are a lot of possible reasons for your air conditioner to turn on, but not cool the air. For central air, some possible causes are the thermostat settings, air filter, condenser unit, evaporator coils, and refrigerant. For a window unit, check the air filter, and check the back of the unit for debris. In many cases when you can’t figure out the cause you’ll have to call a professional.

In this article, we’ll go through some possible causes and fixes for your air conditioning troubles.

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Reasons Why AC Is Running But Not Lowering Temperature

Thermostat Settings

If your air conditioning is running, but not cooling, the first thing you should do is check the thermostat. It may sound silly, but it’s easy to just assume that the thermostat is set like just like it always is. If someone else changed the settings or it the power went off recently, it might need to be readjusted.

If the thermostat is in the “on” setting, it will blow air out continuously. But it may not always be cooling your home. Turn it on “auto”. This will ensure that air only blows from the vents when the air conditioner is cooling.

Blocked Condenser Unit

If the thermostat settings are correct, then your air condenser might be blocked or dirty. Check the unit from the outside, clean around it, and remove any debris that you see around it, like weeds, tree branches, etc. that might be blocking the air circulation.

You can also spray it with a garden hose using a light, gentle stream. A high-pressure stream could damage the condenser fins that allow airflow to cool the refrigerant.

Dirty Air Filter

Check and make sure your air filter is clean. When the air filter is dirty, it could restrict the air to the evaporator coil. This can cause the coil to freeze. You can often find the air filter on the indoor unit.

You might need to change the filter more often, especially if you have pets or run the AC a lot. To test it, pull the filter out. If you can’t see through it, it’s time to wash it or replace it.

If the air still isn’t cooling, you could have a problem with the compressor or refrigerant. You’ll need to call a professional for this.

Wrong Size Air Conditioner

If the AC is only cooling the air slightly, your unit might not be the right size for your home. Any system you get should be able to keep your home cool on the average summer day.

An air conditioner should be able to keep a 20-25-degree temperature difference between the outdoor and indoor temperatures. If you’re not sure of the size, call a professional to determine whether your AC is doing its job correctly.

Frozen Evaporator Coil

Evaporator coils are the part that absorbs the heat from the air of your home. They are usually situated behind a panel on top of the furnace.  Warm indoor air passes through the evaporator coil where heat energy and humidity are removed from the air. Cooler air is then circulated back to the home.

Here are some of the signs of a frozen evaporator coil:

  • Your home is not sufficiently cool when the air conditioner is on
  • Higher utility bills
  • Frost on the copper tubing from inside of the coil cabinet
  • Frost on the exterior refrigerant tubing
  • A significant amount of drainage by the indoor unit

If you suspect a frozen evaporator coil, you will most likely need an HVAC tech to accurately diagnose and fix the issue. In the meantime, you should turn the air conditioner off until someone looks at it.

Circuit Breaker Tripped

Many central air systems have 2 circuit breakers – one for the inside unit and one for the outside. If the breaker for the outside unit is tripped, it will blow warm air into your home. Check the outside breaker and turn it on if it’s off.

If your breaker trips again, you should leave it alone and call a professional. That could be a sign of a bigger electrical issue.

Refrigerant Leak

Refrigerant is the liquid that absorbs heat from the air in your home. If your system is low on refrigerant, the air conditioner cannot absorb enough heat to cool your home. And in the case of refrigerant, if it’s low, you have a leak.

  • Here are the signs of a refrigerant leak:
  • Ice building up on the refrigerant line on the outside unit
  • Warm air coming out of the air conditioning vents
  • A bubbling or hissing noise coming from the air conditioner – this is a sign of a more severe leak.

The refrigerant is made of a chemical called Freon. The EPA limits Freon handling to licensed HVAC technicians. So, if you suspect a refrigerant leak, call a professional.

Leaky Ducts

If there are leaks in your ducts, warm air in your attic can get into the air ducts. This will raise the temperature of the air coming from your air conditioning vents.

Here are some signs of leaky ducts:

  • Higher than normal utility bills
  • Inadequate cooling
  • Your home is unusually dusty (the dust is probably coming from your attic)

Bad Compressor

The compressor is in the outdoor unit. It’s the part that circulates the refrigerant used for heat exchange through the coils of the indoor and outdoor units. In other words, it removes heat from the home and dumps it outside. If the compressor isn’t able to remove the heat from the home, your air conditioner won’t cool your home effectively.

If the compressor is having issues, you will probably have to replace it. They’re hermetically sealed, meaning you cannot open them to repair a single part of it. It is the most expensive part of your air conditioner, so it might be more cost-effective to just get a new one.

Other Causes

There are many components of a central air system, with a lot of moving parts. Therefore, there can be a lot of reasons for your air conditioner to be acting up.

Another possible culprit for AC issues is the condenser fan motor. If the fan motor isn’t functioning, the fan on the outdoor unit can’t help to dissipate heat. This results in the AC not cooling your home.

Also, consider the age of your air conditioner. Is it over 10 years old? If so, you may want to call a professional to check to see if it needs to be replaced or repaired. Weigh the cost of a possible repair against the cost of a new system.

Troubleshooting a Window Unit

Window air conditioning units are a little less complicated than central air systems. If your window air conditioner is on, but not blowing out cold air there are a few common causes.

Air Filter

Like with central air, a dirty air filter is a common issue with window units as well. To get to the air filter in a window unit, pop off the front cover. Most easily pop off, but if you have any trouble, refer to the owner’s manual.

Once you have the cover off, pull the air filter out, which should be sitting behind the cover. If the filter is dirty, sometimes you can clean it with soap and water. In other cases, you’ll have to replace it. Again, check your owner’s manual.

Blocked Air Flow

Another thing to check is whether the airflow is being blocked. Check the back of the unit to see if trash or other debris has accumulated there.

Sometimes, things can get into the back of the AC and disrupt the fan blades. To check the fan blades, you may have to pull off the back case.

Refrigerant/Compressor Issues

If your filter is clean and your airflow is unobstructed, the problem (and the fix) are more complex. For refrigerant problems, you will most likely need to call a professional. Like with central air systems, the refrigerant needs to be handled by an EPA licensed technician.

If the compressor isn’t working, this complicated problem is best solved by a professional. However, it might not be worth it cost-wise. It might be cheaper to just replace the AC than to have a professional come and look at it.

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Related Questions

How do you wash an air conditioner’s filter?

Once you remove the air filter from the air conditioner, clean it with your vacuum. Use one of the attachment wands for the vacuum to remove as much dust and dirt as you can. If that doesn’t fully clean it, you can often wash it in the sink with soap and water. Another option is to soak it in a mixture of vinegar and water.

Why won’t my central air turn on after a power outage?

Your circuit breaker in the AC system probably needs to be reset. First, turn the system off using the thermostat. Next, flip the breaker off for the indoor unit. Then flip it back on. Wait 30 minutes to give the AC’s internal breaker a chance to reset. Leave the thermostat off during this time. After half an hour, you can turn the thermostat on “cool”. The air conditioner should turn back on at this point.

Kathryn Flegal

Kathryn is a craft aficionado who loves writing about DIY home improvement projects. When she’s not writing, she loves reading, listening to musicals, and playing with her kids.

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