AC Troubleshooting: 12 Common AC Problems and How to Fix Them

Air conditioner problems can get you heated, especially if they happen during the peak of summer. You rely on your AC unit to keep your household comfortable, so you want to resolve any pesky AC issues as soon as possible. Here, we’ll walk you through 12 common problems your AC system might have, how to fix them, and when to call in a professional for air conditioning troubleshooting. 

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 several potential reasons why your AC has gone out. Many times, it’s due to a tripped circuit breaker, but the culprit may be faulty wiring in some cases.

Solution

AC unit not working? Check 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 resetting the breaker doesn't work, call in a professional. Don't attempt to open the electrical panel to check for wiring issues. Whenever you’re dealing with electrical problems, you should call a local electrician so that 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. As a worst-case scenario, your air conditioner is too powerful for your home, and it can't determine when to turn on and off.

Solution

If the problem is a dirty air filter or a blocked condenser unit, thoroughly cleaning your system will resolve the issue. But if that doesn’t work, it's best to have a professional assess your home's cooling needs to ensure you have the correct AC size for your living space.

3. Your AC Is Constantly Running

Although your air conditioner should run frequently during periods of high heat, it needs to shut off periodically to give your system a break and prevent it from freezing up. An AC that runs constantly can wear down the system's components and incur a hefty utility bill. The reasons your AC is running could include anything from setting the temperature too low to faulty electrical parts.

Solution

The first step is relatively simple: increase the indoor temperature on your thermostat and see if your air conditioner continues to run. If it shuts off, then your indoor temperature was simply 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 outside.

Solution

Clean your evaporator or hire a local HVAC repair 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 whether you’re living with any allergy sufferers. Before adding refrigerant, have a professional inspect your unit to ensure it’s not leaking.

5. Your AC’s Air Isn’t Flowing

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

Solution

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

6. Your AC Is Leaking Liquid

When troubleshooting air conditioner leaks, there are two potential causes: water and refrigerant. Condensation outside the air conditioner is normal, but you might have a more significant problem if you see brightly colored stains near the unit, condensation in the AC, or water leaking inside your home.

Solution

Turn off the unit and call in the professionals. An R-410 or R-22 refrigerant leak can damage your compressor, which is a costly part to replace. 

7. Your AC Is Having Drainage Issues 

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

Solution

Turn off the unit, consult the user manual to locate the drain pan, and pull it out to check for debris. Clean off any grime and return the drain pan. Examine the drainage pipe for cracks or clogs, and clean out the pipe using a mixture of water and vinegar. 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. This can significantly increase your utility bill.

Solution

Check for ice on the coils. Ice shouldn’t form on your unit, especially in hot temperatures. A dirty air filter could be the problem (which is easy to swap 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.  

Solution

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 experiencing a musty or mildewy smell, which often resolves the issue. That said, odd smells in your home could also be caused by dead animals in your ductwork, clogs, or leaks. The best way to eliminate a musty smell in your home is to hire a professional. You can also prevent smells by having your AC regularly serviced to prevent mold growth.

10. Your AC Is Making Strange Noises

Other than the gentle whirring of the fan, your AC unit shouldn’t make noise. Squealing sounds indicate a belt issue, while grinding noises suggest a motor problem.

Solution

Regular maintenance often catches these issues before they occur, but call a local AC professional if you hear any unusual 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, you may want to check your thermostat. An unlevel or dirty thermostat can trigger short cycling and/or constant running, severely affecting energy efficiency. 

Solution

First, verify that your thermostat's light is on, indicating that it has sufficient 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 when a certain temperature is reached. If these issues persist, call your local AC repair pro for help.

12. Your AC Is Tripping the Circuit Breaker

When a circuit breaker becomes overheated or overloaded, its sensor automatically shuts off power to protect the system—including everything connected to that breaker. If your AC unit keeps tripping the breaker, it could mean the breaker itself is failing or the AC has faulty wiring.

Circuit breakers wear down over time, and breakers more than 25 years old may need to be replaced, especially if they’re powering more modern appliances than they were designed to handle. An overloaded breaker may lack the capacity to support both your AC system and today’s added electrical demands.

Solution

Troubleshooting a tripped AC breaker is usually straightforward. Start by resetting the breaker and allowing about 30 minutes for the system to restart—this often resolves the issue. If the breaker trips again, turn it off immediately. Continuing to run the system with faulty wiring or a damaged breaker can cause serious damage to the AC unit and may require a full replacement.

Unless you’re certified and experienced with electrical systems, it’s best to call a pro to replace the circuit breaker or repair any wiring issues. Working on these components without proper training is extremely dangerous.

When to Call a Pro for AC Problems

You should call a pro for AC troubleshooting in the following situations:

• Your AC unit won’t turn on, and you’ve already checked the thermostat, breaker, and filters.

• The AC is constantly running even after you raise the thermostat temperature.

• The unit is leaking liquid (especially refrigerant or excessive water).

• You notice a burning or electrical odor, or see smoke near the unit.

• You hear unusual sounds like grinding, buzzing, or popping.

• The circuit breaker keeps tripping even after you’ve reset it once.

• You notice warm air, weak airflow, or inconsistent cooling that simple fixes (like changing the filter or adjusting the thermostat) don’t fix.

• Your breaker or wiring is more than 25 years old and hasn’t been inspected recently.

How to Prevent Air Conditioning Problems

Dust, debris, and other obstructions can reduce your HVAC system’s efficiency and wear down its components. As a result, you may see higher utility bills or face costly repairs and replacements. Before you get to the point of needing air conditioner troubleshooting, you can take a few steps to prevent problems altogether. 

Follow these HVAC maintenance tips to keep your system running efficiently:

• Regularly clean your AC by removing dirt, leaves, and debris from around it.

• Replace air filters every one to three months, depending on manufacturer recommendations. 

• Check and clear the condensate drain to prevent clogs.

• Seal any duct leaks to improve airflow.

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

• Clean your ducts if they show signs of dirt or debris, or if you notice poor airflow. 

• Open air vents throughout your home for proper circulation.

• 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, damaged parts, or hear strange noises coming from the unit.