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Why is My Central Air Unit not Working? 10 Quick Fixes

Why is My Central Air not Working? 10 Quick Fixes

The summer is here, and it has brought its ugly friend, the heat. But you are prepared, you run over to your thermostat, turn on the central air, but nothing happens. How could your central air unit betray you and leave you victim to the heat? Well, there are 10 Reasons Central Air Units Break, and they are as following:

why my ac unit isn't cooling

Why is my central air not working?

  • Your Thermostat Batteries are Dead
  • The Indoor Disconnect Switch is Off
  • The Outdoor Disconnect Switch is Off
  • You Have a Tripped Circuit Breaker
  • A Fuse Has Been Blown
  • You Have a Blown Transformer
  • The Starting Components are on the Fritz
  • Your Indoor/Outdoor Coils are Dirty
  • Your Air Filter Needs to be Changed
  • Someone has Damaged the HVAC Components

If any of the items mentioned above have taken place, your Central Air unit will not protect you from the summer heat. In fact, many portions of the Southeast United States only became widely inhabitable because of the invention of Central Air Units. So, trust that we understand your need for a smooth operating system.

Reasons Your Central Air is Broken and How to Fix It

The important thing to remember is that a central air unit is a machine, and every machine needs to be maintained in order to keep it running smoothly. But, even with proper maintenance, a machine will break down in time due to general wear and tear.

However, that is not always the reason your central air unit may have gone out. So, we will break down all 10 Reasons your central air Units Break, and we will give you some tips on how to fix them.

Change thermostat batteries

1. Thermostat Batteries or Broken Thermostat

If your ac unit ever breaks, always check your thermostat batteries. If it is your batteries, this means that there is nothing wrong with your central air unit itself. The best way to tell if it is your batteries is if the thermostat is displaying nothing. This typically means the batteries are out of juice and need to be replaced.

Changing the thermostat batteries out should be your first move when the screen is blank and you are not sure why. Of course, you can always contact your HVAC Specialist for peace of mind. But all it really takes is just a couple of triple-A batteries, and your day will be saved.

However, if your batteries are fine, the screen is on, but no cool air is blowing, this typically means that your mode setting is set to either heat or fan. Switching this mode to cool should fix your problem. If not, continue reading the following scenarios to find your solution.

thermostat for central air

product pricing2. Indoor Disconnect – Off

Many times, this switch is located in one’s garage or attic. If you have been in either one of these locations and have played with any switch that seemed to change nothing, no light or fans turning on, this could have been your indoor disconnect switch.

Or, if you have been moving things around in either of these spaces, it is possible that you could have bumped into it, causing it to turn itself off. Whatever the case may be, all you have to do is simply set the indoor disconnect switch back to “on.” This simple fix may be all that you need, but if it is not, continue troubleshooting here.

3. Outdoor Disconnect – Off

I know what you may be thinking, did they say there is another disconnect switch? And the answer is yes, yes there is. Building codes require that switches be installed next to your air conditioning units, both indoor and outdoor.

So, if the indoor switch is fine, you may want to check the outdoor switch as well. In many cases, storms that come in with the spring result in winds and lightning that may cause debris to come into contact with your unit. If they do, they could have caused the switch to turn itself off.

The solution here is just as simple as the indoor disconnect, just go make sure that switch is located to the “on” position. If the switch is not on the “on” position, make it so, and consider adding a switch cover to avoid this problem continuing. However, if the switch is already placed “on,” you will need to keep on reading to discover your issue.

4. Tripped Circuit Breaker

If there has been any sort of electrical surges, such as from a storm or a power outage, this could have caused one of your circuit breakers to trip. If the breaker that contains the power supply to your air condition unit was tripped, this means the air conditioning unit is simply not receiving power.

To remedy this, all you have to do is find where your circuit box is. Then, check all your breakers for any that could have been tripped. If there are any, and that contains the power supply to your air condition unit, your problem is solved. If this happens on the regular, you can contact your HVAC Specialist about this, or even an electrician. However, if all the breakers are functioning correctly, meaning none have been tripped, then perhaps one of the next scenarios is your problem.

5. A Blown Fuse

A fuse is an electrical device used as a safety precaution. It operates by providing over-current protection to your electrical circuits. If the fuse receives too much of an electrical flow, the fuse blows, protecting your equipment from further damage, by the electrical flow. If you have a blown fuse between your air conditioning unit and your thermostat, the ac unit will not do anything.

Unlike the previous scenarios, this fix is one that should really be done by a central air Professional. However, if a blown fuse is not the problem, the technician will be able to fix any issue that they find. And most likely, that issue will be one of our remaining scenarios.

6. Blown Transformer

Just as the blown fuse, your central air unit will not work if you have a blown transformer. Often times, a blown transformer is the cause of lightning strikes, overheating, wear or corrosion, moisture, power surges, and foreign objects and animals getting too close to the transformer.

This is also not a job that you should take on yourself. Hiring a professional will ensure that nothing else is damaged by the blown transformer, including yourself. This is where you will need a qualified central air company and you might also need the help of a local electrician. The fix includes possibly replacing parts, checking or running new wires, and other like jobs.

hvac components

7. Failing HVAC Components

To properly run, most air conditioning units depend on at least two capacitors inside the outdoor unit. These components, that look like giant batteries, are technically the “start” and “run” compactors. It is the job of the capacitors to hold power and allow your air conditioner to turn on and stay on.

These components are likely to fail due to general wear and tear. If you have noticed that your ac unit struggles to turn on or stay on, this is a likely cause. However, once again, you will need an HVAC Specialist to come to replace these parts. It is the safest way to get the job done.

8. Dirty Coils

If you have properly set your thermostat to the cool mode setting, yet hot air is blowing out of the vent, the likely cause is dirty coils. Coils can be located both indoors and outdoors. These coils can get dirty if you do not have your HVAC system serviced on a regular basis. This servicing can either be conducted by yourself, or by a professional. The important part is to do it on the regular.

But, if you have neglected this, or inherited a dirty unit from your new property, you can try cleaning off the coils yourself or bringing in a trained technician. If you do not do this, your air condition unit will just circulate roughly the same, room temperature, air.

coil cleaner for ac

product pricing9. Dirty Air Filter

A dirty air filter is one of the most common reasons that one’s air conditioning unit is not running very efficiently. Every ac unit comes with instructions from the manufacturer on when to replace the filter, as well as with what size filter. When a filter is left in for too long, it gets very dirty and even clogged, which restricts airflow.

When airflow is restricted to an ac unit, the system literally freezes up. Ice will begin to form on the above-mentioned coils, as well as everything else. And of course with ice forming comes many other issues that could arise, but that is for another article.

All you have to do to fix this problem is to replace your old filter. This alone will help tons. However, you could also go in and clean up all the side effect of a clogged filter, or hire this job out.

central air filter

product pricing

10. Damaged HVAC Components

Lastly, we have damaged caused by time, wear and tear, and by physical abuse. This could cause a leak in your central air system. If there are any components to your HVAC system that are damaged or fail, the rest of the system will not work correctly. And this includes your ac unit.

This damage could be from bumping in the outdoor unit while landscaping, from storms throwing debris around, to even bumping into wires or pipes. But, the best way to make sure every component is good to go, is to hire an Central Air Company to service your entire system. This way you can be sure that there is nothing that goes unnoticed and unfixed.

central air filter change

Summing It Up

Your ac unit is a very important piece of equipment, as it saves you from the summer heat. But, as we have learned, there are 10 Reasons central air Units Break, and that there are many ways you can get them fixed. Those being any of the following:

  • Your Thermostat Batteries are Dead
  • The Indoor Disconnect Switch is Off
  • The Outdoor Disconnect Switch is Off
  • You Have a Tripped Circuit Breaker
  • A Fuse Has Been Blown
  • You Have a Blown Transformer
  • The Starting Components are on the Fritz
  • Your Indoor/Outdoor Coils are Dirty
  • Your Air Filter Needs to be Changed
  • Someone has Damaged the HVAC Components

If any of the items mentioned above have taken place, your Air Conditioning unit will not protect you from the summer heat. But do not worry, there are fixes that you can do yourself, or you can always call in the handy central air Specialist, to get your space back to its proper living temperature.


Written By

Hi there! My name is Matt and I write for Expert Home Report. I enjoy writing about everything related to home improvement, home tips and DIY. In my spare time, I'm either spending time with my family, doing a DIY project or learning a new skill.