What Is An AC Capacitor and Can I Replace Mine

Like most people, you probably don’t think much about your air conditioner’s individual components until they outright fail or exhibit signs of distress. However, knowing what each component does and why it’s important can be key to mitigating developing issues early. If the air conditioner in your Harleysville, PA home is slow to cool things down or impossible to start, the problem may lie with its capacitor. Here is everything you need to know about what an AC capacitor is and when to replace it.

What Is an AC Capacitor?

The motor in your air conditioner needs a jolt of electricity to get going. This short, powerful burst of energy comes from the unit’s capacitor. The AC capacitor stores electricity and sends it to the motor to rev it up just before the start of the cooling cycle. Once the air conditioner is on and in cooling mode, the AC capacitor ramps its efforts down and releases a steady flow of electricity throughout the cooling cycle.

Every AC capacitor is defined by both how much electrical current moves through it and how much energy it can store. The first of these factors is measured in volts. Higher voltage means that the electrical current runs rapidly through the capacitor. A capacitor’s energy storage is measured in microfarads (MFDs). The lowest amount of energy storage that an AC capacitor can have is 5 MFD. The highest is 80.

AC Capacitors Are Both Like and Unlike Batteries

In a way, a capacitor is similar to a battery. It stores power and releases it on demand. However, when a battery goes dead or stops working in any device or appliance, you can simply open the unit up, take the battery out, and put a fresh one in. This is where batteries and capacitors differ. A capacitor is wired directly into an air conditioner. When this unit fails, it takes professional training and experience to get it out without causing damage and without voiding your manufacturer warranty. For those who attempt these projects on their own, there is always a considerable risk of electrocution.

Why Your Cooling System Needs an AC Capacitor

There’s another important way in which capacitors differ from batteries. Batteries are considered a primary power supply when used in devices and appliances. AC capacitors are not. Your air conditioner will only run when the power is on at your residence, and it needs a continual power supply that its capacitor isn’t intended to provide.

In addition to being connected to the electrical system in your home, your air conditioner requires a larger jolt of power for effective operation. Air conditioners require considerable amounts of energy. More importantly, their energy demands regularly exceed the capabilities of a home’s wiring. AC capacitors make up for the difference in energy demand and energy supply by giving the air conditioner’s motor a “kickstart.” This jolt comes at the start of each cooling cycle and ends when the cooling cycle is finished so that the capacitor can begin storing more energy for the next round.

What Happens When the AC Capacitor Fails?

Even when there are no interruptions in your home’s power supply, a broken AC capacitor will keep your cooling system from doing its job. During the hottest portion of summer, this component is one of the most common sources of AC problems. When your cooling system’s capacitor becomes worn out or when it fails outright, your air conditioner won’t be able to cool down your home no matter how long it runs.

AC Capacitors Don’t Last as Long as Air Conditioners

There’s a very common misconception about the expected lifespans of air conditioners. Modern and well-maintained cooling systems can last as long as 20 years. However, this does not mean that all of an air conditioner’s internal components are guaranteed to last as long. Certain parts of an air conditioner will wear out long before the unit itself has reached its end. The AC capacitor is one of the hardest-working parts in your air conditioner. As such, it may need to be replaced one or twice throughout the lifespan of your cooling equipment. In fact, you may even need to change this component more frequently if your home is prone to power surges and you haven’t installed whole-house surge protection.

What Causes an AC Capacitor to Fail?

AC capacitors fail for a variety of reasons. Regular power surges and short circuits are common reasons why these components stop working or fail to work reliably. Direct lightning strikes are virtually guaranteed to render capacitors inoperable. Prolonged exposure to extremely high temperatures can take a toll and so can normal wear and tear. If your air conditioner has been subjected to any jarring impact, such as a falling branch or tree, this can cause AC capacitor damage too.

Common Signs of AC Capacitor Issues

Given that a broken AC capacitor doesn’t eliminate normal power supply to the AC unit, many common signs of a bad capacitor aren’t easily associated with this component. For instance, if your home isn’t getting any cold air while the air conditioner is running, you might assume that you have a refrigerant leak or a blocked filter. Despite having power and being able to continue running, air conditioners cannot cool down building interiors if the capacitor isn’t able to provide the jolt of energy that kicks the cooling cycle into action.

Other common signs of AC capacitor problems include:

• Having the AC turn off even though the building interior is still hot
• Unusually loud humming sounds while the air conditioner is on
• A faint and slightly sweet burning odor coming from the outdoor unit
• Sudden and dramatic increases in your home energy bills

More often than not, if a capacitor has gone bad, all of these symptoms will occur together. Thus, seeing a jump in your energy costs isn’t enough on its own to diagnose a bad capacitor. However, if you have unusual odors at the outside unit, persistent humming noises, and insufficient cooling, you can assume that the capacitor lies at the root of your troubles.

HVAC technicians look for these symptoms, but they also used specialized tools to assess the health and performance of capacitors. If they suspect that your AC capacitor is having trouble or has failed, they’ll measure its voltage, current, and resistance. Even these diagnostic processes can result in serious injury for homeowners who attempt to tackle them on their own.

Some Air Conditioners Have Two Capacitors

Not every air conditioner has a single capacitor. Every central cooling system must have either two separate capacitors or a single, dual-function capacitor in its outside unit. If your air conditioner has two separate capacitors, one will provide a jolt of energy to start the cooling cycle, and the other will provide a continual energy supply to the AC motor until the cooling cycle reaches its end. These are known respectively as start capacitors and run capacitors.

Dual-function capacitors perform both functions. Air conditioners with dual capacitors are often smaller given that there’s less for the outdoor units to house. They are often also easier to diagnose and maintain. In some models with two separate AC capacitors, if one stops working, it may be possible for HVAC technicians to replace both units with a single, dual-function capacitor. This is an upgrade that can cut your future repair costs if the capacitor happens to fail again. It’s a worthwhile investment to make if you live in an area with frequent disruptions to the main power supply and equally frequent power surges.

Although there are many important AC maintenance tasks that you can capably handle on your own, for tough jobs like damaged or failed AC capacitors, you can count on the IT Landes Home Service Team. We provide reliable AC maintenance, installation, and repair services. We also offer heating and plumbing services, and fuel oil delivery. If you’re air conditioner isn’t performing like it should, we can help. Call us today.