Share This Guide
Is your central AC not cooling air? That can be really frustrating especially if you wake up to a hot night. While there could be any number of reasons for your central air not cooling, the following are the most common ones:
- Power issues
- Thermostat Settings
- Tripped circuit breakers
- Low refrigerant levels
- Thermostat wiring issues
- Dirty Air filters
Most of the issues that prevent your ac from cooling can easily be fixed without calling in HVAC professionals. But before we go into details, lets briefly look at how a central AC system works.
How Does a Central Air Conditioner Work?
A central air conditioner works on the same principle as a refrigerator works. It cools your home by using the refrigerant to transfer heat from the indoor air to the outside air. When you set your thermostat to the temperature point you need, and if the indoor temperature goes above that point, your ac will kick into action and start cooling the air inside.
Typically, an air conditioner will have the evaporator coil and a condenser coil.
So, this is how a central air conditioner works like:
- The indoor fan draws air through the return ducts.
- This air passes over the cold evaporator coils and the refrigerant passing inside absorbs heat from this air and turns into gas.
- The refrigerant in gas form, goes over to the compressor where it is pressurized and sent over to the condenser coils. As the refrigerant goes through the condenser coil, it releases heat to the outside air as it condenses.
- The cycle continues until the temperature on your thermostat drops below what you need.
Let’s now dive straight into issues that can prevent your ac unit from cooling your air.
Why Is My AC Not Cooling My Home?
1. Issues With Power Supply
When you are dealing with an ac unit not cooling your house, firstly you want to check if your system is powered up.
When there is no power supply to your central ac system, it won’t turn on to cool your home. For a split central AC system, you will have an indoor unit that is typically installed inside your home and an outdoor unit.
If you had someone recently do some work near your HVAC installation, they might have either switched off the outdoor unit by mistake or intentionally (for safety). And if they did, they would have forgotten to switch it on again.
The split system comes with two power switches, one for the outdoor unit and another one for the indoor unit. The power switch for the outdoor unit is typically installed near the condenser lines that go into your house. If its off, switch it on.
You’ll also need to make sure that the indoor power switch is on. If they are all on but your ac doesn’t cool, then head over to your thermostat and verify that everything is in order with it.
2. Thermostat Settings
Once you verify with the power supply to your ac system and everything is good. Double check the thermostat settings.
Sometimes settings can be adjusted accidentally. Other people that live with you could also have adjusted your thermostat by either accidentally or intentional in order to save some energy.
And if your thermostat is a programmable one, check if it was programmed without error. It’s easy to wrongly program your thermostat especially if you were doing it in a hurry.
If your thermostat was wrongly programmed, reset it and reprogram it.
Depending on your model, you can reset your thermostat by pushing the reset button and holding it for at least 5 seconds before releasing it.
Alternatively, if your thermostat uses batteries, you can reset it by removing the battery and inserting them in reverse for a couple of seconds.
A Low battery could prevent your central AC from responding to temperature changes
A dying battery could also be the reason your ac unit is not cooling. When you have a low thermostat battery, it will affect how your air conditioner will respond to temperature adjustments.
Not only that, with a low thermostat battery, you will have trouble turning on and off your ac unit. An easy solution to this is to replace the batteries with new ones.
3. Tripped Circuit Breakers
After you have checked your power switches and your thermostat, but everything looks great, it’s time to look at the circuit breakers. A split central AC system will typically have two breakers, one for the indoor unit and another one for the outdoor unit.
A circuit breaker can trip if there is power surge, and this happens to protect your equipment from damage. And usually, outdoor condenser units have compressors that use much power, and this can cause breakers to trip from time to time.
All you need to do to restore power is to flip back the breaker. If it trips 2-3 times, there could be something wrong withing your equipment. Call a licensed HVAC technician to come and have a look.
#TIP: Never tape a breaker switch.
Also read: Heat Pump Not Working [7 Easy Solutions]
4. Low HCFC Levels Could Be The Reason For AC Not Cooling
Little or no HCFC could be the reason your AC is not cooling your home. HCFC stands for halogenated chlorofluorocarbon. It’s a chemical that is used as a refrigerant in your AC system. If HCFC leaks out of your air conditioning system, it can severely affect how it works.
If leaks develop within your cooling system, the refrigerant can escape. The refrigerant is a ‘medium’ that is responsible for transferring heat between your indoor and outdoor air. It does this by absorbing heat from the air inside your home and disposing it outside.
When there is little or no refrigerant in your AC system, cooling won’t take place. And that could be the reason for your AC not cooling your home.
Below is what will happen if there is no refrigerant in your cooling system.
- When air is drawn into the ac unit, it won’t cool because there will be no refrigerant to absorb heat from it.
- The fan can continue blowing out air but not cold air
- The compressor will overheat and possibly get damaged.
If you suspect that your air conditioner has run out of the refrigerant, its best you call in professional guys to come and verify the refrigerant charge in your system.
In the meantime, turn off your cooling system as you wait for professionals to arrive.
5. Thermostat Wiring Issues
Another issue that can cause your AC not to cool your home is thermostat that is not wired properly. Each primary function of the thermostat such as heating, cooling has its own wire connection.
Make sure that there are no loose connections too. There is no standard for thermostat wiring colors. So, you can’t tell what colour of the wire to connect to a particulate terminal.
HVAC systems come wiring designation information on the control usually on their control boards. If you are using a Honeywell thermostat, make sure the terminals Y1 and Y2 are connected.
6. Dirty Air Filters
Dirty air filters can cause many issues with your HVAC system. Filters work all the time when your central air conditioner is running. They trap dust, and other substances that you wouldn’t want to go into your air conditioner.
Because they trap dirt, they quickly become dirty and clogged. Dirty air filters limit air flow into your air conditioner. This can cause your evaporator coil to freeze. And you won’t have cooling in your home.
Sometimes, the dirty air will bypass the clogged air filters and find its way to the coil. Then, they will deposit dirt and debris on the coil. Because of this, the refrigerant won’t be able to absorb the heat from your indoor air and eventually you’ll have no cooling in your home. To prevent this from happening, make sure that:
- You change air filters at least once in 2 months
- You have regular HVAC maintenance (ideally twice a year in the Spring and Fall)
7. Covered or Blocked Outdoor Unit
If the outdoor unit is covered with debris and other objects, it can prevent your AC from cooling efficiently. The outdoor unit contains the condenser coil, the blower fan and the compressor.
The compressor pressurizes the refrigerant that is already in gaseous form and sends it into the condenser coils where it disposes off the heat absorbed from the indoor air.
If the condenser unit is covered with leaves, soil or other objects, it can be hard for the system to dispose away the heat. This can mean no cooling for your home.
Read also: Heat Pump Not Turning On [4 Easy Solutions]
8. Stuck Reverse Valve Can Cause AC Unit Not Cooling
When the reverse valve has a problem, it could be the reason for your ac not cooling your home. If your central AC is a heat pump, then you are familiar with a reverse valve.
The reverse valve switches between the heat and the cool mode so that your heat pump can work both as a heater and an air conditioner.
But over time, the reverse valve can malfunction, and when this happens, it can get stuck in one mode, either in heat mode or cool mode. If it gets stuck in the heat mode, you won’t have any cooling for your home.
9. Leaking Duct Work
If your air conditioner is working but not cooling, the culprit could be leaky ductwork. The cool air can leak out of the ducts before reaching your living spaces. Because of that, your ac won’t cool your home.
Another thing to note is that when you are running your air conditioner, ensure that you close the windows, if there are too many openings to the outside, the cooling efficiency of your AC will significantly reduce, and you won’t see the cooling effect by your AC.
10. Blocked Registers and Vents Could Prevent Cool Air From Flowing In
If one room is not cooling when the air conditioner is running, this could be something to do with blocked registers and vents.
Make sure that registers and vents are not closed or blocked. Registers could be closed by accident, and when this happens, no cold air will come through the vents when your air conditioner is running.
Check also if vents and registers are free of any objects that could be blocking them such as furniture and rugs.
Open closed registers and vents and wait few minutes to see if cool air will start flowing in.
11. Blown Out Blower Fan.
The blower fan draws air into the condenser unit so that it can take away heat from the coils. However, if the blower fan is not working, it will be had for the HVAC system to dispose the heat, and so you will likely experience an ac not cooling your house.
12. Dead Compressor
If everything does not work out, you could actually be dealing with a dead compressor. In this case it will need to be replaced with a new one. Compressors are generally expensive. If the cost of replacing your compressor is higher than 50 percent of the cost for buying a new HVAC system, I recommend that you buy a new HVAC system.
We hope that solutions provided to the tips in this article have been helpful to you. After you have tried out these tips, and you have an ac not cooling your house, then perhaps it’s time to call for professionals HVAC repair services. Thank you for reading.
HVAC tech with over 30 years of experience. Retired and doing repair work on the side around Madison County, AL.