AC Won’t Cool Below 74 Degrees [Solved]

If your ac won’t cool below 74 degrees, this can leave you feeling really uncomfortable. With the severe high temperatures that come with summer, when you have this problem, you want to fix it quickly. That’s why we have put together a few common things that can prevent your ac from cooling enough. These include

  • Thermostat Issues
  • Dirty air filters
  • An undersized ac system
  • High outdoor temperatures
  • Opens windows and doors
  • An Ac whose condenser unit is covered or blocked
  • An AC system that is running out of the refrigerant
ac not cooling below 74: A man checking condenser unit
A man fixing an ac condenser unit

Also read: Heat Pump Not Cooling Below 80 Degrees [Solved]

While you can easily fix most of these issues (and we have provided DIY solutions to each), there are a few that will need a hand of a licensed HVAC professional to get sorted out.

7 Possible Reasons Your AC Won’t Cool Below 74 Degrees

1) Thermostat Issues

Thermostat issues are the most common reasons for air conditioners not cooling enough. When you notice that your ac is not lowering temperature to your set point, check your thermostat settings.

Ensure your thermostat is set to ‘cool.’ If the settings are correct, you might have problems with your thermostat wiring.

If you recently replaced your thermostat, try taking a look at the wiring again. Ensure all wires are correctly and firmly connected. You can also check the wiring designation on the control panel of your HVAC system for reference.

2) Undersized AC System

If your ac won’t cool your home to your set temperature, you might be dealing with an ac that’s undersized.  Before buying an air conditioning unit, a technician typically looks at how big your space or home is, then he can recommend that the size of the ac unit buy. However, when the size of your home is not taken into consideration, you might end up buying an undersized or oversized air conditioner.

The cooling power of your ac system is measure in BTUs. It’s easy to measure the needed capacity of your ac unit if you want to get a mini split air conditioner or a window air conditioner. The challenge comes when you want to get a central air conditioning system.

Other times a good-sized air conditioner is be installed but later when you decide to modify your home. Extending your rooms or house without considering the current size of your ac unit can cause issues. That can cause problems with your air conditioner’s cooling.

What to do if you have an undersized ac unit

If you are dealing with an undersized ac unit, there are a few things you can do to boost your ac cooling power. These include:

  • Keeping your indoor environment closed from outside.  If necessary, close open windows and doors. If you are using a ductless mini split air conditioner, ensure that the room from where the ac is installed, is isolated from the others by keeping the room closed
  • In rooms where you have direct sunlight coming through, try closing blinds to avoid radiant heat. Heat from sunlight can make it even harder for your undersized ac too cool your home
  • Get another air conditioner with the correct BTU rating for the size of your home or room. Getting a new air conditioner can be the best option for some homeowners especially if nothing is working to improve cooling. It can also be a good option if the central air conditioner is more than 10 years old.

3) Hot Outdoor Temperatures

Your ac system will have a hard time cooling your home if outdoor temperatures are extremely high. This is also the case during heat waves.  Air conditioners are designed to work properly below 92 degrees and they can only cool a maximum 20 degrees from the outside temperature.

So, if the temperature outside is 95, then you can only expect your ac to cool your home to about 75 degrees. Because of that, excessive outdoor temperatures could be the reason your ac is not cooling below 74 degrees.

Though there is nothing you can do to control your outdoor temperatures, there are a few things you can do to try and bring down your indoor temperature. These include:

  • Turning off heat producing appliance such as stoves. Instead of turning on your oven or stove, make use of grilling outside.
  • Waiting until outdoor temperatures go down before doing laundry or using the dishwasher.
  • Spraying water on the condenser unit with a hose

4) Dirty Air Filters

If air filters are not changed or cleaned on time, they can become dirty and quickly get clogged. When this happens, they will prevent your air conditioner from cooling your home enough.

Dirty air filters could prevent your ac from cooling properly
A dirt filter for a mini split ac

Air filters screen out dirt and unwanted objects from air before it gets into your ac system. This ensures that your system works efficiently and also that the air that Is blown into your home has minimal harmful substances.

However, dirty air filters will restrict air flow into your ac system and that will significantly reduce the amount of air that gets to the evaporator cool. This eventually reduces cooling for your home. To avoid this problem, you need to wash or replace air filters regularly.

How often should I change my AC filter in my house?

Most HVAC filters need cleaning or replacement every 30 -60days. But this can depend on how often you use the ac system, the quality of your surrounding air, number of pets, household size and a few others.

Check the condition of your filter regularly. Some newer air conditioners come with a check filter light, to remind you when you need a filter replacement. Usually, air filters are found near the return vent or at the indoor air handler cabinet.

 Look at the filter and if it has the color of mud, then it’s really time to change your air filter.

TIP: Be sure to check the size of your fitter before getting a new one to avoid compatibility issue.

5) Open Windows and Doors

Open doors and windows to the outside might just be the culprit for your air conditioner not cooling below 74 degrees. This is the case if you are using a room or window air conditioner. For the central air conditioner doors between rooms need to be left open for the even cooling of your home.

But whatever the case, doors to the outside need to be closed. When outside doors and windows are open, hot air from outside will flow in and displace the cooler air. This really makes it hard for your ac to cool your home.

sealing gaps between windows
A man sealing off gaps

Make sure outside doors are closed. If there are gaps between windows and gaps between doors, seal them off too. This can improve your air conditioner’s cooling.

6) Blocked AC Condenser Unit

Another thing that could stop your ac unit from cooling is a condenser unit that is covered with objects and dirt.

A condenser unit is a part of your ac system that handles the disposing of heat that is extracted from your home. This is done with the help of a condenser fan. The condenser fan draws in air from the sides, sucking it through the condenser coils and ejecting it through the top.

When the condenser is blocked, it won’t have enough space­­­­­­ breath out the hot air form your home.

This will greatly reduce the efficiency of your system and your ac will not cool your home as it should.

How often should you clean your outside AC unit?­­­­

Cleaning your outside ac unit can be done about 2-3 times a year but this will depend on how quickly it gets dirty and clogged.

A dirty condenser unit is visibly easy to spot. If your condenser unit has Foliage and other objects nearby, they can quickly build up on your unit and clog the fins and the coil. This will make it hard for the condenser fan to draw in air from the sides.

You can clean your condenser unit by:

  • Using your hose to spray water around it
  • Clear away debris around the condenser unit

Read also: Heat Pump Not Blowing Cold Air [Solved]

7) Leaking Refrigerant

If your ac can’t cool below 74 degrees, it could a sign of a leaking refrigerant. A refrigerant (commonly known as freon) is a chemical that’s used in air conditioning systems for absorbing heat from your home and transferring it outside.

If your system is running low on the refrigerant, your ac system won’t be able to cool your home. With time, and due to various conditions, your system can develop leaks, and this can cause the refrigerant to escape.

How to fix a leaking refrigerant

Fixing an air conditioning system that has a leaking refrigerant can be a little bit complicated for an average homeowner. In this case if you believe that your system is running out of the refrigerant, it’s in order to engage your local HVAC maintenance service providers.

Man gas welding the leaking condenser coil
A man sealing freon leaks

HVAC professionals typically have special tools for investigating the source of freon leak. They will also seal off and test the system before recharging it with any more refrigerant.

How can I make My air conditioner work efficiently?

You can help your air conditioner to continue working better and efficiently by

  • Regularly changing air filters
  • By ensuring that your air conditioner undergoes the annual double tune ups, in the spring and fall
  • By keeping the condenser unit clean and free of debris and other objects

Final Thought

Now that you’ve learnt possible reasons why your ac won’t cool below 74, we hope you have found a solution to this problem. If your ac continues with the same problem after you have tried out our tips in this guide, its perhaps best to call for HVAC professional help. Professionals will have your problem sorted out in no time. Thanks for reading

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