Air Conditioner Not Cooling
AC Troubleshooting Guide

Why Is My AC Not Cooling? 9 Common Reasons

Outside temperatures are spiking. Your air conditioner has been running … yet, your house still feels like an oven. So you ask yourself, “Why is my air conditioner not cooling the house?”

Here are the most popular reasons for your air conditioner not cooling your house down when you need it most.

Click any below to jump to popular solutions and more info

  1. Your Thermostat Is On The Wrong Setting
  2. The Air Filter Is Dirty
  3. The Air Condensor is Dirty
  4. You Have Blocked Vents Or Air Ducts
  5. Broken AC Fan Motor in the Condenser Unit
  6. There Is A Refrigerant Leak
  7. The Compressor Is Bad
  8. Improper Installation Causing Air Duct Leaks
  9. The Evaporator Coils Are Dirty

How to Fix an Air Conditioner Not Cooling the House

Once you have identified the problem, what can you do about it?
Fortunately, there are a number of fixes to these problems that you can do yourself with minimal time, effort, or money.

Do It Yourself Options When AC Unit Not Cooling

Here and common easy DIY solutions when your AC isn’t blowing cold air:

Thermostat on the Wrong Setting

AC Not Cooling - Hoffmann Brothers

  • Common Reasons: This may have the easiest solution to your AC not blowing cold air. If your thermostat is set to Fan, it may be constantly running, but the air conditioner is not cooling to the preferred set temperature.
  • Popular Solutions: Set the thermostat to Auto and double check the set temperature. The fan will kick on as well as cool the air and keep the temperature in your house down to the degree you prefer.

Dirty Air Filter

  • Common Reasons: Have you cleaned or replaced your air filter lately? A dirty air filter could limit the amount of cold air that can filter through and cool your house. Alternatively, it could cause the evaporator coil to freeze, which can also limit the amount of cold air able to filter through and cool your house.
  • Popular Solutions: An easy fix and a good preventative measure going forward is to check your air filter monthly and clean or replace it as needed.

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Dirty Condenser

Air Conditioner is Working but Not Cooling - Hoffmann Brothers

  • Common Reasons: When was the last time you cleaned the condenser — that part of the AC unit outside your home? Now is a great time to start! If you venture outside to find the condenser is full of leaves, weeds, and grass clippings, that could explain why the air conditioner is running but not cooling. This blockage means it can’t properly cool your home by removing all that hot air and replacing it with cool air.
  • Popular Solutions: Spray the condenser down with a water hose to remove the debris, and you may just notice a difference in your home’s temperature. Be sure not to blast the unit with a high level of water pressure, or you will risk damaging it and causing a different, more expensive problem!

Blocked Vents Or Air Ducts

  • Common Reasons: If you were closing your air vents in unused rooms in an effort to conserve energy or save money on your power bill, you may want to rethink those efforts when you find your air conditioner is not cooling the house below 80 degrees. Closing these vents restricts the airflow and doesn’t allow the heat to be properly filtered and subsequently cooled at the optimum rate or pressure it should, causing the units to actually work overtime and cost you more in the long run.
  • Popular Solutions: Open available vents and air ducts

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Broken AC Fan Motor in the Condenser Unit

air conditioner not cooling - Hoffmann Brothers

  • Common Reasons: The condenser unit that houses the fan is typically outside of your home. When the fan won’t turn on or shut off, or the blades are rotating very slowly, it could be dirt inside the cabinet clogging the filter and overheating the unit. It could also be wear and tear or a very hot summer overworking the unit. Sometimes this problem is also linked to a failing capacitor (a separate part) which provides energy to the fan.
  • Popular Solutions: First, make sure thermostat is on, then check for a tripped breaker. You’ll want to also clean or replace any dirty air filters and check to make sure leaves or other debris are not blocking the fan blades. If the problem persists, you many need to call a professional HVAC technician for parts, equipment and service. It’s also important to schedule or perform proper annual maintenance on the AC unit. This is critical when the air conditioner is in regular daily use throughout the hot months.

Refrigerant Leak

  • Common Reasons: An AC running but not cooling the house could be the result of a refrigerant leak due to cracks and holes in the coils due to age, excessive vibration or even contaminants – something that is not good for the unit, your home, or the environment. Every AC unit comes with the manufacturer’s recommended refrigerant charge level, or the amount of refrigerant that should be present at all times.
  • Popular Solutions: Air conditioners do not need refrigerant levels replenished as they do in vehicles; it recycles the liquid which remains in the coils. If refrigerant levels are low, something is amiss and probably leaking. The safest solution is to call upon a professional HVAC contractor who will likely identify and fix the leak, or will replace the cracked coil.
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Bad AC Compressor

AC Not Cooling House - Hoffmann Brothers

  • Common Reasons: The compressor circulates the refrigerant between the inside and the outside units to effectively cool your home. It may fail when dirt or mineral deposits build up on coils, when suction lines get blocked or are the wrong size, when refrigerant and oil lubricant levels are incorrect, or electrical burnout.
  • Popular Solutions: These sometimes require in-depth repairs or replacement and will typically require a licensed HVAC technician for safety and accuracy. Annual maintenance on your AC unit will also prolong the life of your AC compressor.

Improper Installation / Leaky Air Ducts

  • Common Reasons: If your air conditioner was improperly installed from the start, you may have leaky air ducts. This means your AC could be effectively cooling your crawl space – a space you never intened to cooled – but not the rest of your home. That will increase energy costs, invite more dust and prevent cooling.
  • Popular Solutions: Look for any obvious tears in the ducts. Be aware of duct tape on your air ducts. Duct tape is a short-term solution, often fails and it may be a sign of a previous attempt that now needs more attention. Also be sure to check the joints that connect multiple air ducts to verify a proper seal. If you are not able to identify and/or fix the leak, it’s time to call a licensed HVAC contractor for assistance.

Dirty Evaporator Coils

  • Common Reasons: These important and hidden coils absorb the heat from the air in your home and help cool it, but they can get dirty. If dirt and grime has built up on the coils, they cannot function properly and may need a good cleaning.
  • Popular Solutions: This is often a cleaning best done by a licensed HVAC technician with professional equipment, and will typically be addressed during an annual AC maintenance visit.

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Know When To Call a Professional HVAC Contractor

AC Not Cooling - Hoffmann Brothrers
If you’ve worked your way through the above troubleshooting efforts and preventative maintenance measures but still find your air conditioner is working but not cooling your house, it may be time to call in the reinforcements.

The best course of action we can recommend is to assess the situation of the AC not cooling the house, determine whether the problem at hand is one you can apply a DIY solution to or one you should call for some backup. Then get to work or start dialing. Your house will be a much happier home when the air blows cool from your vents!

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