The signs of a bad AC capacitor are sometimes obvious and sometimes so subtle you think the issue might lie elsewhere. The short answer is you may have a failing AC capacitor if you’re experiencing any of the following symptoms:
Your AC system isn't blowing cold air
You hear a humming noise coming from the outdoor unit
Your monthly energy bills increase without clear cause
Your air conditioner shuts off unexpectedly
Your AC unit doesn't turn on at all
You smell something burning from the outdoor unit
Your air conditioner is too old
It's not always easy to tell when your air conditioning system is suffering from a bad capacitor. A faulty capacitor can lead to a higher energy bill and costly repairs if left untreated. Our in-depth homeowner’s guide will break down the most common warning signs to help you handle the situation if it comes up.
7 Signs of a Bad AC Capacitor
This brief overview of the most frequent bad AC capacitor symptoms to look out for when evaluating your AC unit can help you find the right replacement later on.
1. Air Conditioner Not Blowing Cold Air
Is your air conditioner blowing warm air? When the capacitor is bad, warm air blowing through your vents and not cold air is one of the first signs of trouble. You can try turning your condenser unit on and off again, but you may be dealing with a failing capacitor if the problem persists.
A failed capacitor can happen when the air conditioning system short circuits or experiences damage due to the elements.
Replacing your air conditioning capacitor could come at a high cost, but contact a professional HVAC company to test your AC unit before proceeding with repairs or replacement. Proper AC service can determine the root of the issue before any other steps are taken.
2. Humming Noise from Outdoor Unit
A sure sign of a bad AC capacitor is a humming sound from within the access panel. Any humming noises indicate a problem with the air conditioning system or the components of the AC unit.
Try turning the power on and off again to see if it was a one-time issue with the motor or a recurring problem. If you still hear the AC capacitor humming, you’ll need to contact an HVAC expert. A professional will provide a free estimate before discussing the AC capacitor replacement cost.
3. Rising Energy Bills
Another one of the most prominent signs of a bad capacitor on an AC unit is an increase in your electric bills. When an air conditioning capacitor is bad, the unit takes more power to run. Your HVAC system will strain itself to provide cool air, lowering the unit's voltage rating.
Lower voltage wastes energy and money if left untreated. Restore your unit to its full power by contacting professionals to repair or install a replacement capacitor.
4. Air Conditioner Turns Off Randomly
If your AC shuts off without warning, a failing capacitor may be the cause. The air conditioning system should never shut off on its own and will need to be looked at by a professional. While your unit may short circuit now and then without cause for alarm, continuous problems need to be evaluated.
The condenser unit dispels the hot air to keep your home cool, but it can't operate properly if the air conditioning turns off randomly. Of all the most common bad capacitor symptoms, unexpected air conditioner shutdowns are the most concerning.
5. Air Conditioner Does Not Turn On
Another indicator of a bad capacitor is when the system takes a while to turn on or won't turn on at all. This is a clear sign of an issue with the air conditioning system and likely involves the capacitors.
For these situations, have a professional replace the capacitor. Double-check the voltage before you call a professional to provide them with detailed information. From there, they'll be able to assess the situation and determine the best course of action.
6. Burning Smell From Outdoor Unit
You never want to encounter a burning smell from your air conditioning system. This is a strong sign that your system requires repair or replacement to work properly again. Turn your system off, open the windows to vent any potential smoke or chemicals lingering in the air, then contact us for emergency service to fix this problem as soon as possible.
These symptoms may be due to a thin object obstructing the system, normal wear and tear, or overexertion of the system.
If the motor overheats, you may smell something burning. The bearings in the system wear down over time, which can result in parts starting to melt. Some quick fixes, like a technician lubricating the bearings, can temporarily help resolve the problem, but replacement is the best option for a more permanent solution.
7. Age of Your Air Conditioner
The older your air conditioning system is, the more likely it is to break down. Capacitors don't last forever, and an older one is subject to burning out. It’s best to replace your air conditioner every eight to 10 years.
You may notice other issues with your unit, such as the fan not spinning or hearing clanking noises whenever you turn it on (which means you should keep it off until a professional can inspect it). An older system will experience malfunctions for a variety of reasons, and unfortunately, the only real solution is to replace the system entirely.
Do you suspect any of these problems fit your situation? Schedule an inspection with one of our experts and we’ll be happy to provide a second opinion.
Warning Signs of a Bad AC Capacitor: At-A-Glance
Warning Signs | What This Means | Next Steps |
|---|---|---|
Not blowing cold air | The condenser isn’t receiving power | Contact a technician |
Humming noise in outdoor unit | Capacitor is overheating, overloading the wiring and its electrical load | Turn the AC off, then on again. |
Rising energy bills | Your capacitor is short-cycling the unit, using excess energy | Check your unit’s thermostat and air filters |
Turns off randomly | Unsteady power supply running to the capacitor | Contact a technician |
Not turning on | Complete capacitor failure or wiring problem | Contact a technician |
Burning smells | Internal wiring could be melting due to overheating | Contact a technician ASAP |
Old age | Internal parts are too worn out | New HVAC unit needed |
If anything you check doesn’t fix the problem, schedule an appointment online. We provide dependable air conditioning repair and maintenance services to fix common issues like failed capacitors.
What Does an AC Capacitor Do?
Every AC system has a motor. All motors come equipped with a capacitor, which charges and starts the motor, allowing the cooling cycle to begin by initiating the fan blades' movement when the AC turns on.
The cool air you enjoy on a hot summer day is all thanks to the capacitor doing its job and keeping your air conditioning running. You can schedule yearly maintenance to have a professional run capacitor tests to ensure your machine is operating smoothly.
When an AC issue arises, it likely has to do with the capacitor inside most models' AC units. An old capacitor is more likely to break down over time, while bad capacitors require more energy to run.
Start Capacitor vs. Run Capacitor
A start capacitor delivers fast voltage to get your system running. A run capacitor gathers an electric charge, then releases it whenever the air conditioning system needs to run the fan or motor. Some models use a dual capacitor, which combines a start and run model into one place.
Learning the parts of your AC system gives you a better idea of what you can or can’t fix on your own.
If the start capacitor goes bad, but the run capacitor is still working, you’ll have a system that can’t turn on at all. If the run capacitor doesn’t work, but the start capacitor is still receiving power, you’ll have a system that short cycles and can’t stay on for long.
What to Check Before Calling a Professional
Now that you know the signs of a bad capacitor, it’s time to learn what you should and shouldn’t do when troubleshooting. Check out these key areas that could also be contributing to your system’s odd behavior.
Thermostat Settings
Sometimes your cooling system isn’t turning on or blowing warm air because the thermostat settings are wrong. Check your thermostat to make sure it’s not accidentally set to a ‘Warm’ setting or turned off entirely.
If the thermostat is on, you can calibrate it by changing it to different temperatures. Try a lower temperature to see if that gets your system blowing cool air again.
Air Filters
A very dirty air filter can block airflow and cause your system to overheat, triggering a shutdown. Even if your filter is only a little dirty, we recommend swapping it out, then turning on your system to see if the issue resolves itself.
According to Energy.gov, it’s best to change your air filter every month with frequent usage or every few months with infrequent usage to keep your system running smoothly. While very infrequent cooling may do fine with a change every four to five months, two to three months is ideal.
Circuit Breaker
Has your home experienced a power outage or recently gone through a renovation? Your circuit breaker might have gotten turned off at some point, sapping power from your cooling system.
Check your circuit breaker to make sure power is being supplied to your AC. If it’s flipped off, turn it back on, wait a few minutes, then turn your system on to see if power has been restored.
Outdoor Unit Debris
Your outdoor unit might be covered in enough debris to interrupt airflow. The fall and winter months tend to leave piles of leaves, dirt, or packed snow, so clearing off your unit regularly will help your system work smoothly.
One of the most common reasons an air conditioner freezes is because of interruptions to airflow. When you clear off debris, double-check to make sure you’re not seeing any leaks or puddles near your unit. If you see unexplained moisture, get a professional to make sure your system hasn’t frozen on the inside or gotten damaged.
When You Should Turn Your System Off
Leaving your system on when it’s showing signs of a bad AC capacitor will make the problem worse. You could end up making your system fail entirely or put yourself at risk of physical damage.
Keep your system off if:
You smell burning or chemical odors
You see dripping or strange condensation without apparent cause
You hear odd sounds like whining, clanking, rattling, or screeching
What AC Problems Look Like a Bad Capacitor?
Bad AC capacitor symptoms can look a little similar to other issues. Review these common problems that sometimes resemble a dying or failed capacitor:
Frozen condenser coils
Low refrigerant
Physical damage to an outdoor unit
What You Shouldn’t Do with a Bad AC Capacitor
Your system’s capacitors hold electrical charges, so trying to open up your unit and test them could expose you to a dangerous electrical charge. If you suspect you’re seeing warning signs of a bad AC capacitor, avoid the following:
Leave your air conditioner on
Turn your unit on and off (with the exception of testing a circuit breaker)
Try to replace the unit yourself
Only a seasoned technician can safely open, inspect, test, and repair your system. If you see bad AC capacitor symptoms, play it safe and let us help. We offer emergency service and general maintenance appointments for all your heating and cooling needs.
Seeing Signs of a Bad AC Capacitor? Call ARS®/Rescue Rooter®
Now that you know what to look for in a bad AC capacitor, who can you call for assistance? ARS specializes in repairing your air conditioning so you won't have to sweat it.
We offer air conditioning repair and installation to homeowners struggling with their current unit.
Contact us today to schedule service and receive a free estimate. Our team is dedicated to quality customer service and strives to meet your expectations. We look forward to hearing from you!
Frequently Asked Questions
Your AC capacitor is likely bad if your system doesn’t turn on, keeps turning off, or emits strange burning smells. Always contact an HVAC expert if you suspect anything is seriously wrong with your system.
No, you should never replace an AC capacitor. You need to contact an HVAC expert since these internal parts store electricity and can potentially expose you or your family to an electric shock.
While your AC may still work with a bad capacitor, it will struggle to function correctly. Eventually, the system will stop working altogether. Extended use can cause further damage internally.
We recommend contacting a professional to handle the repairs so that you don't risk any damage to your air conditioning.
On average, AC capacitors last up to 20 years with regular maintenance. However, the lifespan of the capacitor also depends on the brand and the quality of the materials used.
If you find yourself needing a replacement, don't cut corners. Research which components will work best for your air conditioning.
