Air Conditioner Running But Not Cooling [Solved]

When you are dealing with an air conditioner running but not cooling your home, that can be a really frustrating experience. But hey, we have provided common possible reasons why your air conditioner could be running but not cooling. These include

  • Thermostat settings
  • Incorrect thermostat wiring
  • Leaking refrigerant
  • Compressor capacitor that is defective
  • Undersized ac unit
  • Blocked condenser unit

Also read: Air Conditioner Outside Unit Fan Not Working

air conditioner running but not cooling
A person checking if cool air is coming out of vents

9 Reasons For Your Air Conditioner Running but Not Cooling

There are a variety of issues that can prevent your air conditioner from working properly. Below are some of the reasons for your ac running but not cooling your home

1)Thermostat Issues

When you notice that your air conditioner is not cooling despite turning it on, you need to check your thermostat. Thermostat issues that could negatively affect your air conditioner’s cooling include incorrect thermostat settings and bad thermostat wiring. Let’s jump right into how each of these issues can affect how your ac works.

a) Thermostat settings

Incorrect thermostat settings can prevent your air conditioner from cooling your home even when your ac is running. Make sure your thermostat is set to ‘cool’ and the cooling point set below the room temperature reading.

To check if cooling is working, adjust thermostat cooling point to the lowest and wait for few minutes to see if cool air will start flowing.  Setting your thermostat to the lowest point doesn’t necessarily mean your ac will become cooler but means that your ac will have extended time in the cooling cycle.

You can even go to the vents. Make sure they are not closed or blocked by objects. Open any closed registers and vents and put your hand over to feel if any cool air is coming.

If no cool air is coming out of your vents, but you have set your thermostat to cool. Find out if the outdoor unit is working. You can check if the condenser fan is spinning or if the compressor is working. If the outdoor unit is running normally, then the problem could be with your thermostat wiring.

b) Thermostat wiring

Bad thermostat wiring could be the reason your air conditioner is running but not cooling your home. 

Did you recently install a thermostat by yourself? If so, open your thermostat and check that every connection was done correctly. You can also find the reference for wiring designation in the compartment for the circuit control board of your HVAC system.

Check the wiring designation and make sure everything is firmly connected. Don’t leave any loose wires. If you are using a Honeywell thermostat, you may find this article useful. For all other brands, you can call your thermostat’s manufacturer support for further assistance.

2) Your AC System May Need a Reset

If the circuit control board of your air conditioner is not responding to cooling adjustments on your thermostat, your ac system may need a reset to get your control board to respond. How to reset your air conditioner depends on the model of your air conditioner.

But the universal method of resetting any air conditioner is by tripping the breaker for a few minutes before flipping it back. This should reset your air conditioner. For resetting any specific model, refer to your user manual with specific instructions.

Also read: Home AC Not Blowing Cold Air

4) Leaking Refrigerant

A leaking refrigerant is among the most common reasons for an air conditioning system not cooling.

Air conditioners use the refrigerant to cool your indoor air. Without it your air conditioner can never cool your home. Let’s briefly look at how the refrigerant brings about cooling in your home.

  • Your ac indoor unit houses the evaporator coil, and your outdoor unit has a condenser coil. The refrigerant runs through a network of coils between the evaporator coil and the condenser coil.
  • While passing through the evaporator coil, the refrigerant will absorb heat from the indoor air that passes over the evaporator coil. Heat from indoor air will be transferred to the refrigerant and the refrigerator turns into gas.
  • Then this gaseous refrigerant will go to the compressor where it will be pressurized and sent over to the condenser coil. At the condenser coil, the gaseous refrigerant will dispose heat and condense back into liquid. From here the cycle continues until the temperature in your home falls below the set point.

How will a leaking refrigerant cause no cooling in your home?

Now that we have looked at how a refrigerant is used to cool your home. It will be easy to understand how a leaking refrigerant will prevent cooling in your home.

When refrigerant is leaking from your air conditioner system, you won’t have any cooling in your home because there won’t be heat transfer between the indoor air and the outdoor air.

Solution to a leaking refrigerant

If you believe you have a leaking refrigerant, turn off your air conditioner to prevent your compressor and other components from damage. Then call a local HVAC professional to come and assess the problem. HVAC professionals will be able to pinpoint the leaks using their special tools. They will also be able to recharge your air conditioner with a refrigerant if necessary.

5) Blocked Condenser

A blocked condenser unit can significantly affect the cooling efficiency of your ac system.  When your condenser unit is blocked by dirt, soil or other objects, the fan won’t be able to draw in as much air to take away the heat. Because of that, the cooling of your home will be affected.

A blocked condenser unit can easily be cleaned by using a hose to rinse it. You can also clear areas around the condenser unit to prevent the debris from accumulating around the condenser unit.

6) Dead Capacitor

A dead compressor capacitor can be the reason your ac outdoor unit running but not cooling your home. Newer ac units are equipped with dual capacitors. The dual capacitors cater for both the fan and the compressor. When one side of the compressor becomes defective, let’s say the compressor side of the capacitor dies, the other side for the fan will continue running. Because of that, you may have your air conditioner running but not cooling your home.

6) Dirty Air Filters

Dirty air filters will restrict the amount of air flow around the evaporator coil, and this will affect cooling in your home. Air filters work all the time when your air conditioner is running. They catch dirt, dust and other substances and prevent them from getting to your evaporator coil.

However, when filters are left unchanged, for a long, the dirty air can bypass them and deposit dirt on the evaporator coil. Build up on the coil will restrict the absorption of heat from your indoor air by the refrigerant and the coil may start to freeze up.

To prevent this from happening, always remember to change filters at least once in 2 months or as recommended by your manufacturer.

7) Disconnections In The Ductwork

Leaks or disconnections in the ductwork can be responsible for no cool air coming into your home when your ac is running. The cold air could be escaping before cooling your indoor living spaces. Check your ductwork in the attic and try to find leaks,

Leaks can be sealed by using the duct tape. If you can’t find the leaks, a call to a professional HVAC technician is in order.

8) Undersized Air Conditioner

An air conditioner that is too small for your room or home can be the reason your ac unit it not cooling. Let HVAC experts come and find out if that is the issue and what size of an air conditioner you need. Alternatively, you can use online tools for air conditioner/room sizing

9)Some Windows Are Open Inside Your House

When windows and doors are open in your house, your air conditioner won’t be cooling even if it is running. The warmer air from outside will come in and displace the cooled air. When running an air conditioner, you need to make sure the doors and windows of your home are closed.

Final Thought

Having looked at the possible reasons for your air conditioner running but not cooling, the next time you are dealing with this issue try going through out tips before calling in HVAC professionals. You might just save yourself that service call.

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