Air Conditioner Not Cooling: Why Is My AC Not Working? AC Problems

Air Conditioner Not Cooling: Why Is My AC Not Working? AC Problems

If you’re having general issues with your AC not working or not cooling, here is a list of 10 common air conditioner problems and solutions.

A common question we hear is why is my air conditioner not cooling? But unfortunately, there is no such thing as a quick fix. There could be several causes for air conditioning problems, which is why we’ve put together a home air conditioners troubleshooting guide to help you spot potential issues, make adjustments where you can or seek a professional’s help.

From common problems with AC units to more complex issues that require qualified experts, it can be incredibly helpful to get to know more about your system to prevent future problems and increase your AC’s lifespan.

If you’re having general issues with your AC not working or not cooling, here is a list of 10 common air conditioner problems and solutions.

Cleanliness of Your System

If you’re consistently coming up against AC issues, make sure you’ve checked the unit for debris and replaced any dirty filters. Not only will a dirty system be less efficient but it will also affect the units lifespan and your overall energy costs. In all cases, proper annual maintenance services and checks are the best way to prevent problems.

Thermostat Errors

It might not always be a problem with your unit, sometimes a good place to start if your air conditioner has stopped working is with your thermostat. If the thermostat is not calibrated properly it may be telling your AC not to turn on. The best way to test your thermostat is to set it to the lowest temperature setting and see if the system starts.

Still no luck? You may need to recalibrate the thermostat or replace it entirely. Having a trained HVAC engineer do this for you is best, however, your thermostat may have come with a manual that will help you programme it yourself. If in doubt, get the experts in as programming anything is not always an easy task.

Listen Carefully

Whenever it comes to air conditioning repair troubleshooting, the focus can easily be on what you FEEL, but what you HEAR could be just as important. If your system is becoming noisy and the fan motors seem to be getting louder and louder it could be that there is dirt or debris caught in them.

Alternatively, noises could become more prevalent if the elements are becoming worn – belts and bearings in particular.

If the noise persists or you hear anything out of the ordinary, we recommend turning your AC unit off and calling an engineer. If you persist, you could cause irreversible damage to your system.

Human Error

It’s easy to blame technology when something doesn’t seem to be working, but if you plan to troubleshoot air conditioners of any kind, the important test is to make sure you’re operating the system properly.

It is very common that people expect their units to work efficiently despite the fact windows or doors are kept open. Read your user’s manual if you are not quite sure about the proper operation and handling your unit requires.

Condenser Problems

If you are experiencing a hotter environment than you expect despite the setting on your thermostat, the issue could be with your condenser coils.

The condenser transfers the heat from the air to outside the building, which means if it is dirty the heat transfer will be less efficient and the unit will have to work harder to compensate for this.

Best thing to do is clear your coils of any debris and soot and note if you see an improvement.

Check your Refrigerant Levels

If your struggling with your AC not working and not cooling, a common air conditioner problem could be that your refrigerant levels are too low. Low levels of refrigerant results in a humid environment, with a unit that is neither efficient nor performing properly.

There could be two reasons for low refrigerant – you may have a leak or it may have been undercharged during the initial installation.

Checking your manual or confirming with your HVAC engineer to see if the refrigerant charge exactly matches the manufacturer’s specifications is vital for a healthy running system which is as efficient as possible. A system that is overcharged or undercharged is only going to cause issues.

You must be very careful about adding refrigerant to a system if you don’t know how full it already is. If you top up the refrigerant and the problem persists, it may be time to get a qualified HVAC engineer on site to locate the issue and fix any leaks if they exist.

Is Your Drainage Cleared?

In order to make the air feel cooler, AC units remove moisture from the air and lower the humidity. However, in order to remove the moisture, there must be a way of transferring the liquid away from the environment.

The drainage systems installed on air conditioning units are designed to take water via a drain line and into a pan which will be drained away. Issues begin to arise if the drain becomes blocked, so always ensure you check the drains on your system whilst running through your air conditioner troubleshooting process.

If you forget to check your drains, a blockage could result in water filling up and backing up into the unit itself, causing severe damage.

Another element that affects drainage, can be whether the drain was level when it was mounted. Have this looked into if you have any cause for concern?

Damaged Ducts

If your AC doesn’t seem to be cooling your building, common air conditioner problems can be caused by a lack of air flow through the ducts.

If you have leaky air ducts which can be caused by wear and tear, animals or damage from works that have occurred during or after installation, the cooled air will be escaping into the walls of your building.

Ducts that are leaking will result in a less efficient system that costs you more and leaves your home warmer than you desire.

Electrical Failure

Air conditioning repair troubleshooting isn’t just about working with and understanding the mechanical elements. Electrical faults can occur too which are not uncommon reasons for any air conditioning not working.

If the AC is turned on and off (done frequently where units are too large for their buildings) regularly it can cause compressors and fans to wear out.

Another electrical element that can expire quickly is wires and terminals. These should be checked in your annual HVAC service by a professional – just another reason to take part in regular planned preventative maintenance regimes.


Similar to the thermostat, your sensors must be checked. If they are not measuring the right temperature of the air that is coming into the system then it will not be adjusting the air properly. You may end up with an air conditioner not cooling at all or one that is too cold and in a constant cycle.

Rather than recalibrating, like you would a thermostat, a sensor may be corrected by simply checking it is in the right location. Adjusting its position carefully so that it is close to the coil but not quite touching it is best – however always check your manual as different manufacturers may have different specifications.

In Conclusion

In places like the US where most houses have AC installed, the average household’s energy spend on cooling alone is around 6% according to

That’s a huge figure when you consider the other running costs that a home can incur and when you look at the bigger picture. Our duty is to ensure industrial and home air conditioning systems are running safely, efficiently and cost-effectively, so we hope this air conditioner troubleshooting has helped you trace and prevent issues.

If you continue to encounter air conditioner problems, please seek an HVAC professionals help immediately.