Why Air Conditioner Not Blowing Cold Air But Running?

We all know that the air conditioner’s main job is to make your house cooler. If you ever notice that your unit is no longer blowing cold air, it might be an indication that there is something wrong with the system.

Incorrect thermostat settings, clogged filters, leaking refrigerant, blocked registers, and problems with the evaporator coil and condenser – all these issues can make your cooling unit stop blowing cold air. Window air cons can get clogged with dust and debris, so that should be one of the first things you check.  

Why Air Conditioner Not Blowing Cold Air But Running?

A thermostat issue

Make sure that your thermostat is set to ‘cool’. If it’s set to ‘fan’, the unit won’t be cooling the air that it’s circulating.

Do bear in mind that for the thermostat to send a signal to your AC, the room temperature has to rise above the control setting. Until then, your system won’t be cooling.

A dirty filter

A clogged filter affects the airflow. If there is not enough air entering the system, the coils won’t be able to work as efficiently (or they might simply freeze up).

As a result, your house won’t be getting enough cold air, even though the system is running (it might even be overworking, at this point).

Leaking refrigerant

The refrigerant is essentially the substance that allows your air conditioner to cool. This medium is able to extract heat from the air and then release it outdoors.

The refrigerant doesn’t get used up when the system is running, but if there is a hole in the coils, the substance can start leaking.

Small leaks are usually relatively difficult to notice. The inability to effectively cool the air is one of the symptoms.

The others include hissing sounds, frozen coils, increased humidity, and AC leaking water.

Issues with the evaporator coil or condenser

Coils can freeze up or get dirty. They are also prone to problems with mold and mildew and, of course, these components can wear out over time.

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The same can happen to a condenser.

As the coils and the condenser are the components that handle the refrigerant and make it move, any problem related to them can cause a lack of cold air.

Blocked registers

If your return air registers are clogged or blocked, the system won’t be receiving enough air. If the supply vents have an obstruction in them, they won’t be able to supply your house with conditioned air.

Make sure that nothing in the room is blocking the vents (like furniture, for example), check the ductwork for any leaks, and take the vent cover off to have a quick look at the ducts – you might see debris.

Read: How Do Smart Air Conditioners Work?

Window Air Conditioner Not Blowing Cold Air But Running

Bear in mind that if your unit is sitting in the window and it’s sunny outside, the hot outdoor air might be counteracting the AC’s cold air.

You should also inspect the back side of the unit – this is exactly where a lot of debris and dust might accumulate. Check if there is anything that is preventing the blades from turning.

If you have spotted something, open the case and give the AC a clean.

Read: Why Window Air Conditioner Compressor Not Turning On?

How Do I Know If My Air Conditioner Is Cooling?

If your air con is the correct size for your house, then it should take the unit around 15-20 minutes to start cooling the space. Do bear in mind that if the day is particularly hot or if you have decided to choose a very low setting, then it might take the system a bit longer.

By the way, cooling a house that had time to get hot will take longer as well.

On average, it should take the central AC unit around 3 hours to cool a standard 4-bedroom house by 10 degrees Fahrenheit.

If you want to test you unit’s cooling ability, then follow these steps.

  1. Replace the filter and remove the covers of the vents that you’re going to test.
  2. Figure out where the supply and return ducts are (when you place a tissue over a return duct, the tissue will get sucked into it).
  3. Turn the air con on (set the thermostat quite a few degrees below the current room temperature). Let the unit run for at least 10 minutes.
  4. Locate the supply and return ducts that are closest to the AC unit.
  5. Tape a thermometer inside the supply duct, wait for about 10 minutes, and record the temperature. Do the same with the return duct.
  6. Calculate the difference between the temperatures – it should be at least 20 degrees. If it’s not, then your unit is not blowing cold air and there is something wrong with the system.

How Do I Fix My AC Not Blowing Air?

  • Check and reset the thermostat
  • Replace the filter
  • Clear the condensation drain, if it’s clogged – locate the end of the line and carefully clear out the clog with a narrow item
  • Examine the ductwork – seal any gaps and refit the ends of the loose joints (if there are any)
  • Clean up the area around the condenser (outdoor unit) – make sure that there is nothing on top of the unit and keep the area around it clean (2 feet in all directions)
  • Clean the coils – if you don’t feel comfortable performing these kinds of tasks, make sure to call a professional.

Read: Why Air Conditioner Heat Mode Not Working?

Should I Turn Off AC If It’s Not Cooling?

Give the air conditioner enough time. It might simply need another hour or two.

Check the thermostat settings and take a look at the filter, replace the thing if it’s dirty. Also, make sure that nothing is blocking the supply vents.

If none of these tips helped, then there might be something wrong with one of the internal components. In such a case, the safer option would be to turn the AC off and invite an expert to take a look at the unit.

How Do I Reset My Air Conditioner?

Another thing that you can try to do if your air conditioner is not blowing cold air is reset the unit.

  1. Turn off the unit at the circuit breaker and flip the AC’s power switch to the ‘off’ position.
  2. Locate the reset button and hold it down for around 5 seconds before releasing it.
  3. Turn the unit back on.

Read: Why Does My Air Conditioner Smell Musty?

Where Is the AC Reset Button?

You can consult the owner’s manual to find out where your air conditioner’s reset button is located.

You might find the red button on the outside unit (along the bottom edge) or inside the indoor unit (right behind the service panel).

How Long Does It Take for an AC Unit to Reset?

The unit will not reset as soon as you push the button. Once you turn the system back on, it is going to need at least 30 minutes to reset the air con’s internal circuity. 

Turn the unit on at the thermostat after half an hour had passed. Set the device to at least 5 degrees below the room’s temperature to be able to find out if your air con started blowing cold air or not.

Read: Why Does Air Conditioner Run At The Same Time As A Furnace?