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Why Is My Air Conditioner Not Working? 10 Possible Reasons

why is my air conditioner not working 10 possible reasons

This post was originally published on June 1st, 2022, and last updated on June 1st, 2023.

Even the best air conditioners can have issues. Waiting in a hothouse for a professional to come and fix your AC isn’t anyone’s ideal option. Fortunately, our troubleshooting guide can help you know how to identify some common air conditioner issues. There is a difference between your AC not working and not cooling and we help you sort the two with the goal of getting your AC pumping out sweet cool air quickly.

Why Is My Air Conditioner Not Turning On?

No matter what type of system you have – central, mini-split, ductless, or heat pump –  there are commonalities between the types of AC systems that our troubleshooting guide covers. If your air conditioning system just isn’t turning on then we suggest you run through a few things before calling in an HVAC expert:

  • Make sure the outdoor breaker fuse is positioned correctly
  • Check your electrical panel for a tripped breaker
  • Confirm that your thermostat is switched on
  • Check for a clogged air filter
  • Check your condensate pump for proper operation

If you check these and all is in order then read on for other solutions to AC problems.

Why Is My Air Conditioner Not Cooling the House?

Uneven temperatures throughout your home are not uncommon. If you have been noticing different temperatures in rooms or higher energy bills there are a few common causes with some easy solutions. 

Your Thermostat is Not Set Properly

One of the simplest things to do is check your thermostat setting. If your thermostat is set incorrectly then your AC isn’t going to work. Check to make sure it is not set to heat or that the temperature isn’t set too high.  

Your Air Filter is Dirty

A dirty air filter can impede the flow of air and can cause a host of problems. Short cycling is when your air conditioner turns on and off again in very short bursts without completing a full cooling cycle. When filters are blocked your AC unit has to work harder, creating higher energy bills and unevenly cooling your home. It may even cause your air conditioning system to stop working. Regularly cleaning or changing your air filter will help you avoid a future problem or you can save money and stress with routine maintenance.  

Blocked Vents are Reducing Air Flow

Blocked supply vents are another reason your AC unit isn’t putting out enough cold air. Check your vents to make sure there isn’t dirt or dust build-up that could be preventing airflow. Toys, furniture, or closed dampers may also be the problem. Rearrange furniture away from registers and check for obstructions that may have fallen into your ducts by accident. 

Why Is My Air Conditioning Fan Not Working?

If the fan on your AC unit stops working it could be something as simple as your circuit breaker tripping or something more complex. If your air conditioning fan isn’t working your HVAC system won’t cool your home. 

Burnt Out Condenser Fan Motor

An air conditioning fan motor is a fairly uncomplicated part but if it doesn’t work then your home isn’t going to be cool. Because the fan works hard, it gets a lot of wear and tear which can lead to a burned-out motor. Intermittently running fans, slow-turning fan blades, or a fan that won’t turn can be a sign the motor has an issue. This is a time when you will need to call an HVAC technician. You can prevent AC fan motor burnouts by regular maintenance and reducing dirt and dust in and around your system. 

Capacitor is Failing

No, the capacitor isn’t a time-traveling device. Start and run capacitors are devices that send energy to the fan motor and power the air conditioning unit when energy is needed. These small but mighty workhorses keep your system working properly so that your AC unit doesn’t come to a grinding halt. When it does you may hear a humming from your AC without it actually starting – that is your start capacitor telling you it is time to call in an HVAC pro. If your system is short cycling, randomly shutting off, or delaying AC it may be your run capacitor failing. Again this isn’t something you can fix yourself. Call an HVAC technician for help.

Condensate Pump is Failing

Checking the condensate pump is a fairly easy DIY test. Condensate pumps typically have shorter lifespans than air conditioners and furnaces as they run for both cooling and heating (depending on furnace efficiency). These pumps usually have a test button. Make sure there is some water in the basin and press the test button to ensure it pumps the water out. A failing or failed condensate pump will often trip the furnace so that it won’t run and create a pool of water wherever the furnace is (eg. basement or worse, the attic).

Why Is My Air Conditioner Making Noise?

Air conditioners, when they are functioning optimally, are pretty quiet. There can be the occasional noise when they complete a cycle but if they suddenly start squealing, hissing, buzzing, rattling, clicking, or banging – you get the picture – then it is time to do some investigation. Rattling or banging could mean something has come loose, while buzzing often means you have an electrical issue. Any kind of persistent noise is a cry for help from your air conditioning unit. Turn off your AC and call an HVAC professional to come out and assess your system for issues. 

Why Is My Air Conditioner Not Turning Off?

The opposite of your air conditioner not coming on – not turning off – is also a sign of a problem. If your air conditioner is constantly blowing it puts a huge amount of stress on your system, leading to high energy bills and a shorter life span. Beyond checking your thermostat that it is at a realistic temperature, a couple of other things could be the cause. 

Frozen Evaporator Coil

This could be a sign that you have a refrigerant leak somewhere. Because your AC system can’t get the temperature of your home to ideal it will keep running indefinitely. This is something that needs to be dealt with immediately. Turn off your system and call an AC repair consultant right away. 

Dirt on the Condenser Coil

Yep. That pesky dirt can cause havoc everywhere in your system. The condenser coil’s job is to disperse heat outside your home. If dirt has built up, heat will be trapped inside the air conditioner and keep your system running to reach the target cooling temperature your thermostat is calling for. 

Read next: Best Time to Schedule Air Conditioner Maintenance

Can I Reset My AC?

Most professionally installed ACs will not have reset buttons. Power outages or surges, while rare in the Pacific Northwest, can be the reason your air conditioner isn’t working, however, they will typically come back on as long as you have power. 

Still, after a power outage, it’s a good idea to check your system and your breaker box. Your circuit breaker could have been tripped for your AC or furnace, so it’s important to check both places. A key indicator is that if the thermostat is blank, the furnace might not have power.

Try turning your AC off at the thermostat and resetting your circuit breaker. Wait half an hour before turning it back on. If you are still having difficulties it’s time to call in the professionals before it becomes a worse problem.

Read next: How Long Do AC Units Last & When to Replace Them?

When to Call an HVAC Professional

Safety is always the first priority. When you have hit a wall in your troubleshooting measures it is time to contact a professional. Trying to “limp along” is just potentially causing more damage to your system that will increase repair costs. If in doubt, turn off your system and contact Jacobs Heating & Air Conditioning for help. 

Additional reading: The Role of Air Conditioning in the Fight Against Climate Change

How Jacobs Can Help

If you are looking for help troubleshooting your air conditioning system, our consultants at Jacobs Heating & Air Conditioning can examine your system and determine what repairs need to be made. If you need air conditioning maintenance we are ready to help you save money and keep surprise breakdowns away. You can schedule your next tune-up and keep the stress and hassle out of maintaining your system. No matter what you need we’re always just a phone call away. You are welcome to review our statement on COVID-19 and how we’re taking precautions to protect you, our team, and our communities.

About the Author

Amanda Jacobs portrait

Amanda Jacobs, Internal Project Manager

Amanda Jacobs is an Internal Projects Manager and 3rd generation member of Jacobs Heating & Air Conditioning. She received her MBA from Seattle University and has worked for a leading HVAC training and consulting firm. When not talking HVAC on the Jacobs Blog, you can find her on the golf course or whipping up her famous vegan chili.