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Air Conditioner Fan Not Spinning but Hums

an AC unit

When you turn on the air conditioning at home, the hottest, most insufferable days are instantly better. But sometimes, the AC refuses to run. A common problem is the fan not spinning but humming. If you’re dealing with this situation, you likely have a faulty capacitor.

Knowing what a capacitor is will help you understand its role. You can rely on HVAC specialists to fix your capacitor problems. They have the tools and expertise to perform the necessary repairs or replacements. Your AC will soon be up and running again, and everyone at home will be in a better mood.

Air Conditioner Fan Is Not Spinning But Hums: The Capacitor Might Be to Blame

First things first, it’s helpful to know what a capacitor is. The capacitor is a small cylindrical component inside your AC’s outdoor unit, typically resembling a tin can. Think of it as a giant battery for your AC that stores energy. When you turn on your AC, it provides the first powerful jolt of electricity, kickstarting the blower fan, fan motor and compressor.

Large appliances like air conditioners require five to six times more energy during startup, so the capacitor plays a crucial and strenuous part. While it will lower its energy output once your AC is running, it will continue to supply the unit with power throughout the cycle.

Like any other electrical component, AC capacitors can fail over time and lose their ability to hold a charge. This usually happens when they’ve suffered damage, like exposure to high voltage or temperatures. When a capacitor fails, the outdoor fan motor can no longer start, unable to move the heat inside your home to the outside. You might also hear a humming sound.

Here are some other signs of a capacitor gone bad:

  • It has a swollen top that looks like a mushroom.
  • Its bottom is rusted or corroded.
  • It’s leaking fluid.
  • The AC unit shuts off on its own randomly.
  • You notice smoke or a burning smell coming from the AC.
  • You can’t feel cold air while the AC is on.
  • You have unreasonably high electricity bills.

How to Fix a Faulty Capacitor

The best solution is to contact HVAC experts and let them replace the capacitor. While a capacitor might look like a battery, you can’t just swap it out for a new one. Replacing it involves dealing with high voltage. You must have the proper tools, training and experience to perform a safe and successful replacement. Let the pros handle the situation.

They will shut off the power to the AC and discharge the capacitor of its stored energy to prevent accidents. Once they have safely removed the old capacitor, they will install the correct replacement and attach the wires.

Contact an HVAC professional immediately if you notice any signs of a failing capacitor. Ignoring the issue will strain the motor, which will keep trying to start up without the capacitor’s help. Eventually, it will burn out, and you’ll have a more expensive problem.

an AC unit

Can an AC Capacitor Run the Fan But Not the Compressor?

When it’s boiling in the summer, you will quickly notice if your AC isn’t performing its best. One odd issue homeowners might encounter is when the AC compressor in the outside unit isn’t running, but the fan blades are still turning. A faulty capacitor is a possible culprit behind this problem.

The capacitor powers the blower motor, outer fan and compressor. If it has trouble communicating with the compressor, it won’t run, while the other components will. The best way to resolve this issue is to call in an HVAC specialist. Using a multimeter, the HVAC technician will test your AC’s capacitor and replace it if it’s faulty. While it’s a straightforward fix, don’t attempt it yourself because of the capacitor’s high voltage.

There are other possible reasons the compressor won’t run, including the following.

Dirt Buildup

As your AC pulls in air from your home, it also collects dust, dirt and debris. Most of the dirt gets stuck on the air filter but eventually goes to the condenser coils. With dirt buildup on the filter and coils, there will be restricted airflow in the AC system, and your unit can’t function efficiently. Eventually, the compressor might shut down, while the fan might still be able to turn. Make it a habit to replace the air filter every three months to enhance airflow and prevent compressor issues.

Incorrect Thermostat Settings

Fixing the problem might be as simple as adjusting your thermostat’s settings. Check its temperature and ensure it’s on “auto” and “cool.” That way, the compressor and fan will kick in to achieve the desired temperature for your home. Contact an HVAC professional if that doesn’t resolve the problem. The technician will assess your thermostat and install a new one if it’s broken. They can also help with other thermostat issues, like if your thermostat is flashing cool on.

Tripped Breaker

If your compressor won’t work but the fan is still running, the electricity might not be reaching the outdoor unit where the compressor is. You can confirm this by checking the breaker box and seeing if the circuit tripped. If it did, reset it. If there are no tripped circuits, inspect the wires connecting the indoor and outdoor units and see if there are any loose connections. If you’re unsure, let an HVAC specialist take a look and fix any electrical issues.

Faulty Compressor

Compressors are hardy components, able to last 12 to 15 years. But just like any AC part, they eventually burn out. That’s likely the issue if your AC unit is older than a decade. An HVAC professional can examine your compressor and see if it’s worth replacing or if you should purchase a new AC unit.

an air vent

What Does It Mean When the AC Takes a While to Get Cold?

The whole point of having air conditioning at home is to enjoy instant relief on hot days. But if there’s an issue, your AC might take longer than usual to deliver cooling comfort. If you’re tired of waiting for your AC to cool down your home, you might want to look into these issues.

Clogged Air Filter

You can’t blame your AC for being slow if you haven’t replaced its air filter in months. A clogged air filter hampers airflow inside the unit, causing your AC to run longer to achieve your desired temperature. Aside from slowing down your AC, a dirty air filter leads to many other issues, like overheating, wear and tear and higher bills. You can prevent all that unnecessary stress by replacing it every three months. You might have to do so more often if you have furry loved ones in the family.

Dirty Coils

Your AC has two sets of coils, each with a crucial part to play in the system. The evaporator coil is in the indoor component, absorbing the heat in the air. Meanwhile, the condenser coil is in the outdoor unit, releasing the absorbed heat outdoors. If either of these coils is dirty, it will take your AC longer to absorb or release heat. That explains why it’s taking longer than usual to cool your home. These coils are fragile and hard to access, so let an HVAC professional clean them.

Refrigerant Leak

Refrigerant is the liquid substance that flows inside the evaporator and condenser coils, absorbing and releasing heat. If the coils develop a leak, your AC will lose its refrigerant and be unable to do its job. The only solution is to call in an HVAC specialist. Refrigerant leaks are no joke. Prolonged exposure to refrigerant can have health consequences, so never attempt to fix a leak yourself.

Old Unit

If your AC doesn’t work as fast as it used to, it might be because it’s nearing the end of its life. Air conditioners can only perform at their peak for 10 to 15 years. If your unit is older than that, it’s probably time to let it rest and purchase a replacement. An HVAC professional can install a new unit for you and ensure it’s running efficiently.

Leave Your AC Woes to an Experienced Professional

There’s nothing more frustrating than an AC that won’t turn on when you need it the most. But you don’t have to stress. Let an HVAC professional resolve your AC issues.

ABC Can Keep Your AC Working Efficiently

Dealing with AC issues requires lots of technical know-how. Instead of trying to figure it out yourself, contact ABC Home & Commercial Services. Our professionals can efficiently diagnose your AC problem. They can also offer advice on when to replace your air conditioner.

Tom Riggs

Tom Riggs is the Division Manager for Mechanical Services, overseeing sales and operations for HVAC, Plumbing, Electrical, Appliance Repair and Water Quality for all ABC Austin branches. He joined ABC in 2014. Before ABC, he was an HVAC Service Technician, HVAC Comfort Advisor/Sales and Operations Manager. Tom attended Universal Technical Institute. He's an avid outdoorsman and enjoys country living with his wife and two sons.

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