Air Conditioner Troubleshooting: 12 Common Problems and Tips to Fix Them

Paige Bennett
Written by Paige Bennett
Updated March 31, 2023
Homeowner lowers temperature on the thermostat
Photo: Angelov / Adobe Stock


  • AC units can experience several issues, from not turning on to making strange noises.

  • Short-cycling units could be a sign of debris or a clog in the system.

  • An AC system running nonstop could be an electrical problem, which requires a pro to fix.

  • Regular maintenance and inspections can prevent many common AC problems.

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Air conditioner problems can get you heated, especially if they happen during the peak of summer. You rely on your AC unit to keep you and your household comfortable, so it makes sense that you’d want to get to the bottom of any pesky AC issues as soon as possible. When you need to embark on some good old-fashioned air conditioner troubleshooting, we’ve got your back. 

We’re going to walk you through 12 common problems your AC system might have, how you can fix them, and when to call in a professional. 

1. Your AC Won’t Turn On

What if your air conditioner goes out and refuses to turn on? It’s frustrating, and there are many potential reasons your AC went out. But many times, it’s due to a tripped circuit breaker. In some cases, the culprit may be faulty wiring.


AC unit not working? Try checking your fuse box to see if the circuit tripped. Step to the side of the breaker box (not directly in front of it) and turn the correct circuit breaker switch to the off position (an electrician likely labeled them according to the rooms in your house and the appliances they’re connected to). Then, switch the breaker back on. 

If you do this and there doesn’t seem to be any problem, do not attempt to open the electrical panel to check for problems with the wiring. Whenever you’re dealing with electrical problems, you should call a professional so you don’t end up with a nasty shock or a house fire.

2. Your AC Is Constantly Turning On and Off

This process is called short cycling, and it happens when there's a dirty air filter, evaporator, or clogged condenser unit. Short cycling can cause severe damage to your compressor. Worst case scenario, your air conditioner is too powerful for your home, and it can't figure out when to turn on and off.


If the problem is a dirty air filter or a blocked condenser unit, thoroughly cleaning your system will take care of the problem. But if those fixes don't work, it's best to have a professional come out and assess your home's cooling needs to ensure you have the correct AC size for your living space.

3. Your AC Is Constantly Running

Though your air conditioner should frequently run during periods of high heat, it’s important that it shuts off from time to time to give your system a break and make sure it doesn’t freeze up. An AC that runs constantly can wear down the components of the system quickly and rack up one hefty utility bill. The reasons your AC is running could include anything from setting the temperature too low to faulty electrical parts.


The first step is pretty simple here, and that’s to kick up the indoor temperature on your thermostat and see if your air conditioner continues to run. If it shuts off, great; your indoor temperature’s just set too low. If it continues to run, you should call in a local HVAC repair company. The cause could be any number of things, including a broken thermostat, compressor, or electrical parts.

4. Your AC Is Not Blowing Cool Air

A nice, warm breeze can be lovely, but not when it’s coming from your air conditioner. If this happens, lower your thermostat by five degrees and see if the air cools. If that doesn’t work, there are a few possible reasons why your AC is blowing hot air:

  • The evaporator is dirty.

  • The air filter is dirty.

  • Refrigerant levels are too low.

Scorching hot days can also impact your unit’s effectiveness, especially if you’re trying to cool your house to 65 degrees Fahrenheit when it’s 100 degrees Fahrenheit outside.


Clean your evaporator or hire a pro to do it. Make sure you’re changing your air filter every month or two, depending on your climate, pets in the home, and if you’re living with any allergy sufferers. Before adding refrigerant, have a professional look at your unit to make sure it’s not leaking.

5. Your AC’s Air Isn’t Flowing

Residential air conditioner units installed in the yard
Photo: Maudib / iStock / Getty Images Plus / Getty Images

This problem can manifest in two ways. First, you may hear your unit running with no air coming through the ducts. Second, air is making its way through the ductwork, but it’s not cold. One of three problems is usually causing these scenarios: 

  • Tripped circuit breaker

  • Worn blower belt

  • Low refrigerant levels


Something as simple as a tripped circuit breaker can cause inadequate airflow, so check your fuse box first using the steps outlined above. If it’s not your fuse box, you should call in a professional to inspect your system and see if there are internal problems. They’ll be able to diagnose whether or not you have a worn belt or a refrigerant leak, which could happen if the Schrader HVAC valve breaks.

6. Your AC Is Leaking Liquid

When it comes to air conditioner troubleshooting for leaking liquid, there are two potential causes: water and refrigerant. Condensation outside of the air conditioner is normal, but if you see brightly colored stains near the unit, condensation in the AC, or water leaking inside your home, that indicates a bigger problem.


Turn off the unit and call in the professionals. An R-410 or even an R-22 refrigerant leak can cause damage to your compressor, which is a costly part to replace. If it’s exceptionally hot when you’re facing this issue, we also suggest taking a trip over to your local (air-conditioned) fast food restaurant for a cold ice cream cone while you wait for the professionals.

7. Your AC Is Having Drainage Issues 

AC units have moisture that needs to drain out from the system. The condensate moves through a drain pipe to a pan and finally out to a drain. But the drainage pipe or the drain can become clogged from dirt and debris, which can then cause water buildup in the unit. This can cause serious problems and major damage to the AC unit.


Turn off the unit, consult the user manual to find the drain pan, and pull out the pan to check for debris. Clean any grime off and return the drain pan. Check the drainage pipe for cracks or clogs, and use water and vinegar or water and bleach to clean out the pipe. Fully dry the pipe with a clean cloth. 

If you can’t locate the drain pipe, call in an AC repair professional to help you safely clean out any clogs or repair cracked pipes.

8. Your Condenser Coil Is Freezing

If you run your AC continuously without giving it a break, the condenser coil could freeze. If your condenser coil is freezing, that can wreak havoc on your utility bill.


Check for ice on the coils. Ice shouldn’t form on your unit, especially not in hot temperatures. A dirty air filter could be the problem (which is an easy fix; just swap it out), but you should still have a pro evaluate your system to make sure nothing major is malfunctioning.

9. Your AC Smells Funky

Your AC unit shouldn’t have a stench. If it does, something has likely gone awry. Two types of unpleasant smells seep from troublesome air conditioners: electrical and musty.  


If you smell an electrical odor, turn off your system immediately and call a pro, as this could be a sign of a short circuit, meaning your wires could be burning. This is not something you can fix on your own. 

You can change your air filter if you're getting a musty or mildewy smell, which often solves the problem. However, odd smells in your home could also come from dead animals in your ductwork, clogs, or leaks. The best way to get rid of a musty smell in your home is to call a pro, and you can keep smells away by having someone regularly service your AC to prevent mold.

10. Your AC Is Making Strange Noises

Other than the gentle and oh-so-relaxing whirring sound of the fan, your AC unit shouldn’t make noise. If you hear squealing noises, that’s usually a belt problem. Grinding noises indicate a motor problem.


Regular maintenance can usually catch these issues before they happen, but call a local AC professional if you hear mysterious sounds. These are tricky issues to fix, and you risk breaking the unit if you try to DIY.

11. Your Thermostat Is Malfunctioning

If your AC works intermittently or shuts off after a short period of time, you might want to take a look at your thermostat. An unlevel or dirty thermostat triggers short cycling and/or constant running, which severely affects energy efficiency. 


First, check that your thermostat light is on, indicating that it has ample battery power to operate properly. Then, wipe it clean of dirt and debris, which can affect its ability to signal the unit to turn on or off after reaching a certain temperature. If these issues persist, call your local AC repair pro for help.

12. Your AC Is Tripping the Circuit Breaker

When a circuit breaker is overheated or overloaded, it has a sensor that will shut the system down, which also shuts down everything connected to the breaker. When the AC unit is tripping the circuit breaker, it could simply mean the breaker is having issues or the AC unit has faulty wiring.

Circuit breakers can wear down over time, so breakers over 25 years old may need to be replaced. The breaker may just have too many modern appliances or systems connected to it without having the capacity to power the AC system and these additional technologies.


AC troubleshooting for a tripped breaker typically isn't too complex. You can start by resetting the circuit breaker and giving the system at least 30 minutes to restart; this works for many people. However, if the circuit breaker continues to trip after you try resetting it, shut it off. If you let the system continue to run with faulty wiring or a damaged circuit breaker, it could cause the whole AC unit to fail, in which case you’d have to replace it entirely.

Unless you have extensive experience and certifications working with electrical systems, you should hire a pro to replace the circuit breaker or repair faulty wiring in the AC unit. Inexperienced troubleshooters shouldn’t take on this task, as it can be incredibly dangerous. 

Additional Maintenance Tips to Avoid HVAC Problems

HVAC systems work hard to keep us warm in frigid winters and cool on sweltering summer days. But dust, debris, and other obstructions can make the system work less efficiently or even wear down parts of the unit. In turn, you could see higher utility bills or face costly HVAC system repairs or replacements. Before you get to the point of needing air conditioner troubleshooting, you can take a few steps to avoid problems entirely. Follow these HVAC maintenance tips to keep your system running efficiently:

  • Clean your AC by removing dirt and clearing debris away from the outside unit.

  • Replace air filters every three months.

  • Clear clogs in the condensate drain.

  • Seal duct leaks.

  • Turn off the system when you don’t need it.

  • Clean your ducts if they show signs of dirt or debris

  • Open air vents throughout your home.

  • Get your unit inspected yearly and have a pro perform regular preventative maintenance.

  • Hire an AC repair company near you for quick repairs if you find any leaks or damaged parts or hear strange noises coming from the unit.

Amy Pawlukiewicz contributed to this piece.

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