Inside your AC’s outdoor unit, one of the most important components of your HVAC system is housed. If you look in there, you’ll see a whole bunch of wires and a small, canister-type component that resembles a battery. That’s your AC capacitor. That little piece of equipment does a very big job for your HVAC system.

The AC capacitor is responsible for providing all the energy to your AC system’s motor to cool your home. This small part has the power to stop your HVAC system in its tracks if it malfunctions or fails. Your AC will have to work harder to circulate cool air in your home which will, in turn, eventually wear out your HVAC unit and can result in higher energy bills.

A word to the wise: AC capacitors are high-voltage parts that are dangerous to work with and they should not be handled by an unlicensed HVAC professional. To prevent injury or even death, you should always call a trained and licensed HVAC technician for both diagnosis and repair.

Even though we suggest hiring a professional who is trained and licensed to handle the diagnosis and replacement of a bad capacitor, we like to keep our customers informed. At Dolphin Cooling and Heating, it’s important to us that you understand not only what we do to fix your AC system, but also why. We know that finding a trustworthy contractor who has your best interests in mind is hard to do these days. So to find out all you should know about the AC capacitor and learn how to recognize early signs that there may be trouble, keep reading.

How Does an AC Capacitor Work?

An air conditioner capacitor is to your AC unit’s motor kind of what a starter is to your car’s engine. It provides the initial, powerful jolt of electricity to the motor of the air conditioner that it needs to start running. The difference between a car’s starters and an AC’s capacitor is that, unlike a starter, once that burst of energy is provided, the capacitor continues running. But instead of a steady feed of high voltage, it reduces its energy output and provides a much lower, steady current of power until the cooling cycle finishes.

Capacitors look a lot like batteries and even have similar functions, but they are defnitely not batteries. AC capacitors are high-voltage devices that could seriously harm you because they are connected to wiring inside your air conditioning system which is connected to your home’s electrical grid. AC capacitors also store energy, similar to a battery, which is why they are dangerous even if the power is turned off.

An AC capacitor’s power is measured in both voltage and microfarads. Microfarads represent how much electrical current the capacitor can store, which typically ranges from 5 microfarads (MFD) to 80 MFD. Voltage shows how much electrical current is currently moving through the capacitor at the time of testing. The more voltage in your capacitor, the faster the electrical current is moving through it. A healthy capacitor will both store the appropriate amount of current and allow the appropriate amount of current to flow through it.

How Many Capacitors Are in an AC Unit?

Not all HVAC systems are designed the same. Some are built to run on two single capacitors and others run using a dual capacitor in the outdoor unit.

Systems that require two single capacitors simply have two capacitors to do the job that a typical dual capacitor does on its own. Two single capacitors, one start capacitor, and one run capacitor perform the functions separately. Whereas the dual capacitor performs both functions, delivering the initial jolt of electricity to start the cooling cycle and then converting to a steady state flow of low voltage electricity to continue to run the cycle.

With two single capacitors, if one fails it can be replaced individually. Since the start and run capacitors have different jobs, it is possible that one will wear out faster than the other. If one of these parts fails, your experienced HVAC contractor may decide to replace a bad capacitor with a dual capacitor.

Why Does Your AC Need a Capacitor?

Your HVAC unit requires a lot of power to do its job and do it effectively. Your home’s wiring can’t provide the amount of power the AC unit needs all on its own. The capacitor compensates for your home’s lack of adequate power by kicking in with that boost of energy the system needs. When your AC is not cooling, the capacitor takes a break until it’s time for the next cooling cycle.

Failed capacitors are one of the most common reasons for air conditioner malfunctions, especially in a subtropical climate like southwest Florida’s climate. Capacitors have a strenuous job, especially during the summer months when your air conditioner runs through far more frequent cooling cycles.

How Long Do AC Capacitors Last?

Most will last 15-20 years. Living in SWFL, the life of your AC capacitor could be a little shorter. If your AC capacitor experiences any of the issues below, it will not last the full anticipated lifetime of the part.

Signs of a Bad Capacitor

Knowing the signs of a bad AC capacitor can help you get it diagnosed and repaired before the damage gets to extensive. Some of the common symptoms of a bad capacitor include:

AC Blower Won’t Turn On

The AC blower motor will not function without the blower capacitor. Part of the start capacitor’s job is to kickstart that blower motor. This is a sign that your capacitor is bad, but keep in mind that there are many other reasons an AC blower fan might not be turning. You will need a qualified technician to diagnose the issue properly.

Rising Energy Bills With No Explanation

When the AC capacitor has failed there will be an improper amount of voltage that forces the other air conditioner components to work harder than they are intended to work. This reduces your air conditioner’s efficiency and spikes energy demands, resulting in high energy bills. Your bill will continue to rise until your AC system fails completely or the replacement of the ac capacitor is completed.

A Loud Humming Noise From the Outside Unit

The AC’s blower motor makes a humming sound hums because of the magnetic field generated by the motor’s windings. The energy from the power supplied to the motor causes the motor to vibrate. The humming noise gets really loud if the motor’s capacitor is bad because the energy that would normally go toward spinning the motor has nowhere to go. The energy is trapped and begins producing heat instead. If your outside unit is making a humming sound while the blower fan is not turning, you should shut off power to your AC unit completely until a repair is made to avoid further damage to your HVAV unit.

AC Turns Off Randomly

If your Ac unit’s capacitor is failing, your AC system may not sustain enough current to stay running through its cooling cycles. Turning off randomly, or short cycling is something commonly experienced with an old capacitor or with a capacitor that has malfunctioned.

AC Experiences “Hard Starting”

If your AC capacitor is bad it can cause hard starting. Hard starting is when the AC compressor has a hard time starting up and shudders as its powering up. This can also be a sign of your compressor going bad but, again, this is something a professional technician will have to diagnose.

AC Won’t Turn On at All

Capacitor failure can prevent the AC from turning on at all. Without enough power to jolt the unit into running, your unit will not be able to turn on at all. Like all other AC symptoms, this can be caused by other things as well, all of which HVAC techs can inspect and diagnose for you.

Smoke or a Burning Smell From Exterior Air Conditioning Components

The same issues that cause your outdoor unit to make a loud humming noise will cause smoke or a burning smell once they have been going on for too long. Immediately shut off power to your HVAC unit if you see smoke or smell something burning. Contact your HVAC contractor as soon as possible avoid further damage.

What Causes a Capacitor to Fail?

There are various causes of a bad AC capacitor, but some of those causes can include:

Extremely Hot Temperatures

Overheating is a main cause of a failed start capacitor. Start capacitors are not able to dissipate the heat associated with continuous operation. They are made to operate only momentarily while the AC motor is starting. If extreme temperatures keep the start capacitor working too long, it will overheat.

Wear and Tear

Over time, sustained long-term use of a capacitor is sure to cause failure, like anything else. A failing capacitor isn’t always an old capacitor, but most of the time this is the case unless you end up with a faulty capacitor from the factory.

Short Circuits in the Cooling System’s Wiring

If you’re AC has a short circuit in any of its electrical components, it can cause the capacitor to fail. A short circuit is an unintended electrical connection that sends a high ripple current into the capacitor, causing it to overheat and usually resulting in the failure of the component.

A Power Surge

A power surge is basically an overload of power. Power surges can easily cause damage to any electrical components in your HVAC system, including your capacitors. A surge protector can help prevent this from happening.

Lightning Strikes

A lightning strike is basically a power surge on steroids. Lightening can fry or severely damage any of the electrical components of your AC unit quickly and easily. A surge protector can help protect your HVAC unit from lightning, although it cannot protect it 100%. The only thing that can protect anything with electrical components from lightning is to have the power disconnected entirely.

Storm Damage

Damage to the outside unit from debris caused by high winds or flooding during a storm can damage the capacitor in your outdoor unit. If you notice issues with your AC after a storm, clean up the debris surrounding your unit and contact your HVAC contractor.

How to Test an AC Capacitor

You can’t know for sure that your AC capacitor is the problem without testing it. Again, handling an AC capacitor is dangerous and is not something the homeowner or anyone who isn’t licensed should be doing. An HVAC professional will use special tools and training to test the capacitor’s voltage, current, and resistance.

Always hire a professional to do the testing of your AC capacitor. A worn-out AC capacitor can cause more damage the longer it’s not working, which is not something you want to deal with. If you suspect your AC capacitor is not working well or at all, call your HVAC contractor for an appointment.

When our technicians are called to test your AC capacitor, they will access the interior of your condensing unit where they will look for the source of the problem. If they see any of these signs of a bad AC capacitor, they will know to investigate the component further:

  • Cracks
  • Bulging
  • Oozing liquid from the capacitor and circuit board
  • Not enough charge when tested with a multimeter

How Much Does an AC Capacitor Cost?

The cost to replace your AC capacitor will vary depending on the AC unit you have and your location.

Can I Replace an AC Capacitor Myself?

No, you cannot replace or repair an AC capacitor yourself. Just like testing, the replacement of these parts is a dangerous job that requires training. There are many components of AC maintenance that you can perform yourself, but this is not one of them. For your safety, please contact a qualified technician to correctly and safely remove your failed capacitor and replace it with a new one.

Hiring a Professional to Install a New Capacitor

Having AC issues is never any fun. The good news is, you can call Dolphin Cooling and Heating for the resolution of those HVAC issues. Your HVAC technician will be able to properly diagnose your AC’s failures and recommend a course of action. If you have a failed ac capacitor, your technician will know the type of capacitor that you need for replacement. They will recommend the appropriate type of capacitor from the options available for your unit, either dual-run capacitors or single run capacitors.

A resolution for your higher energy bills or an AC unit that won’t cool or run properly is just a phone call away. Our helpful staff is standing by to listen to the problems you’re facing with your AC unit and help you by discussing possible solutions. If you need a service call, we will get you set up with your appointment. Our experienced technicians are always on the road in Naples and the surrounding areas, ready to serve our community.

What Our Customers Are Saying

We appreciate our customers and their feedback! If you’re looking for an HVAC company that will treat you like family, contact Dolphin Cooling today!

“Being a business owner by time very tight. They did everything they could to come out on time showed up early to resolve the problem. Brandon was awesome. I will recommend them to anybody. Donald Bishop Salt live Transportation owner.” – Allen

“Jason was very professional and thorough when he inspected and started up my HVAC system. Couldn’t ask for a better technician.” -Jerry Rein

“They saved me money and time and they went above and beyond. Ian knocked my brand new AC unit over and mangled my air handler up on the flat roof (from another company) so it froze up the compressor. I had the original AC company out and had them rebuild the handler and fix the electrical but I wanted a second quote on the compressor with installation so my coworker referred me to Dolphin. I appreciate how quick and professional the phone staff (Nikki) and the salesperson were professional! I recommend Dolphin Heating and Air Conditioning.” -Pamela Pike

“After Hurricane Ian passed through and our electricity came back on, the air conditioner would not work, called around and Dolphin Air was able to have a tech, Jason, from the Cape Coral office come the very next day ((Sunday)! He fixed the issue and was such a pleasure to work with, experienced, professional, and courteous and we truly appreciate this company and how they run their business! We signed up for a maintenance plan and look forward to Jason being our tech going forward!” -Rich and Cheryl Stout

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