What Are the Most Common Causes of a Noisy AC

Posted on by meister

As you read this article, you’ll learn helpful information about what causes an AC unit to hum without running:

    • Why the root cause is usually a faulty capacity
    • How to temporarily fix this issue
    • What you can do to prevent this problem

If you live in the East Valley area, you know a functional AC is essential to comfort. So when something goes wrong, you need to get it repaired as soon as possible.

In many cases, a broken AC unit simply won’t turn on. But there are a few instances when you may think it’s running but find your home isn’t cooling off. What can you do beyond searching “my ac hums & buzzes but won’t run?”

The best thing to do is arm yourself with knowledge. The sooner you understand what’s going on with your AC, the sooner you can remedy the issue.

What Are the Most Common Causes?

The good news is, if your system sounds like it’s running, there are only a handful of issues it could be. However, this is only true if your AC is “humming” or “buzzing” — if you hear squealing, screeching, banging, or other loud, strange noises, the issue may be more complicated.

If you suspect something’s wrong with your HVAC system, it’s best to contact a professional, such as Superstition Cooling. Trained technicians know exactly what to look for, so they can quickly spot an issue and get your HVAC up and running as soon as possible.

AC Unit Motor

In rare cases, your unit motor may be out. This motor is responsible for powering the parts that circulate air, which is why no air will be coming out of the vents.

Capacitor

Most of the time, this issue is caused by a bad capacitor. What is a capacitor? It’s a mechanical part responsible for starting the unit. Without a capacitor, the following AC parts can’t get moving:

    • Blower fan
    • Fan motor
    • Compressor

The capacitor itself holds energy, which it uses to jump-start the cooling process. Why do you need what is essentially a battery if your AC is hooked up to the electrical system? Starting up an HVAC system is more complicated than simply running it, as the process requires up to six times as much energy. The capacitor provides this energy, so there isn’t a strain on your electrical system every time your air conditioner kicks on.

So, what happens when a capacitor goes bad? There are several signs a capacitor is no longer up to snuff:

    • Leaking fluid
    • Rust or corrosion
    • Swollen top

Typically, capacitors last about 20 years, which is longer than a typical AC unit lasts. Theoretically, you should replace your unit before a capacitor issue ever shows up. However, there are extenuating circumstances that can cause capacitors to fail before their time.

Because capacitors are essentially batteries, they have a chemical composition that allows them to hold a charge. High temperatures can affect these chemicals, decreasing efficiency and accelerating corrosion. Electrical surges can also burn out capacitors if the voltage exceeds what the component can handle.

How Do I Fix It?

The best way to repair your AC depends on what’s wrong. For example, if the root cause is a defunct unit motor, that will require a replacement part at the very least. However, since this issue is common among aging units, other problems may need addressing. When you tally up the repair costs, it may be more cost-effective to upgrade your unit.

On the other hand, if the root cause is a bad capacitor, you have a few options: the long-term solution and the short-term solution. The long-term solution, of course, is to replace it, while the short-term solution is to do the capacitor’s work yourself.

Replace It

You have to replace a bad capacitor eventually. There’s no way around that. For your unit to work as it should, it needs immense energy, and it won’t get that without a capacitor.

The good news is, a professional can easily replace the broken part. It’s essential you reach out to an HVAC company for this process because the new capacitor must be compatible with your AC unit.

Give It a Kickstart

Do you have to suffer in the East Valley heat while waiting for a technician to arrive? Fortunately, no. There is a workaround to get your air conditioner working temporarily.

Essentially, you play the part of the capacitor by “jump-starting” the AC fan. You can do this by turning your AC on, then manipulating the fan blades with a thin rod until they start spinning by themselves. This solution involves taking the outer casing off your AC unit every time you want to cool off, so it’s only recommended as an emergency measure until you get the capacitor replaced.

How Can I Prevent These Issues?

Of course, you want to save money and discomfort, so it makes sense to take precautions against issues that can put your AC out of commission. Fortunately, there are several steps you can take to ensure your AC unit motor and capacitors have long, smooth-running lives. 

That said, know that these parts will eventually break down from wear and natural deterioration. Units typically last around ten years, so if your system is older than that, it’s time for a replacement.

Get Regular Maintenance

Yearly maintenance is crucial to keeping your air conditioner functional. A trained technician can spot a problematic capacitor before it goes bad.

Buy an HVAC Surge Protector

Since high voltage can render capacitors dysfunctional, you can prevent damage with an HVAC surge protector. This equipment blocks excessive electricity from running through your AC unit, which can happen during high grid usage or storms.

Invest in Energy Efficiency

We know there are certain times you absolutely must run your AC — heatstroke is a real danger here in the East Valley. However, the less you run the air conditioning, the better. Every time your unit clicks on, it gets a little more worn, so forgoing the AC when possible can prolong its life.

What Sounds Should I Listen For?

You know what your AC should sound like when it’s running. If the thermostat shows the unit is on, but you don’t hear air in the ductwork, something is wrong.

The next step is to check the unit itself. While it’s running, you should hear a similar sound of air movement. However, when there’s a problem with the AC unit motor or a capacitor, you’ll still hear mechanical noises, but not the familiar rush of air. Typically, these sounds are described as a “hum” or a “buzz” caused by vibrating parts.

When your HVAC system is on the fritz, you need professional help. Superstition Cooling has served the East Valley area for nearly a decade and offers 24/7 emergency services, so you don’t get stranded in the heat. Our technicians are always courteous, and their experience means the issue gets fixed quickly.

In addition to repair, we also offer maintenance and installation services. To learn more or get an estimate, give us a call at 480-983-7407 or visit us online.

Featured Image: Cunaplus M.Faba/Getty Images