My Air Conditioner Hums and Buzzes But Doesn’t Turn On: A PHX Tech Explains

First, you hear your air conditioner click on but only feel warm air coming from your vents. The outdoor AC unit is humming like normal, but the fan isn’t spinning, and you hear a buzzing noise coming from the unit.

If this describes your situation, you most likely have a bad fan capacitor. A damaged capacitor will prevent the AC fan motor from receiving power. Then, the system can’t transfer and dump heat from inside your home outdoors, which is why you feel warm air blowing out of your vents.

In this blog, we’ll answer these common capacitor questions:

We’ll cover a quick short-term fix that can help keep you cool until you can get your air conditioner repaired. But first, let’s start with defining the purpose of a capacitor.

A fan capacitor is a small, cylinder-shaped metallic object mounted to the side of the outdoor air conditioner unit. It typically resembles a tin can or a 9-volt battery. Its purpose is to act like a giant battery and store energy as “extra” juice for the air conditioner. Large electrical appliances like an air conditioner need almost 5-6x the energy it uses while continually operating during start-up. This tremendous amount of needed energy is why we recommend homeowners turn back their thermostats instead of shutting off their AC systems to prevent wasting energy and money.

When the air conditioner turns on, the capacitor provides a jolt of electricity that kickstarts the compressor, the outdoor fan motor, and the indoor unit’s blower fan. All of these are required for proper air conditioner function and to keep the system running continuously.

Just like a battery or any other electrical component, capacitors can weaken and lose their ability to hold a charge over time. This usually happens after they suffer some sort of damage. For example, a capacitor exposed to high temperatures or high voltage will have a shorter lifespan.

When the capacitor no longer works properly, the outdoor fan motor will fail to start. Your air conditioner will then no longer be able to move heat from inside your home to the outdoors, explaining the warm air coming from the vents.

The best way to tell if your capacitor has damage is to inspect it visually. Signs that your capacitor has gone “bad” include:

• A swollen, “mushroomed” top
• A rusted or corroded bottom
• Fluid leaking from the part

Now, we’ll review what you should do with a broken capacitor.

Need a quick fix for your failed fan motor capacitor? Turn on your air conditioner and take a long, thin object (like a stick or screwdriver) to push the fan blades inside the outdoor unit. Please make sure to take proper safety precautions when doing this so that nobody gets hurt.

This manual push should provide the “kick” the fan motor needs to start running. However, remember that the capacitor only helps to start up the fan motor; it doesn’t actually keep the motor running. If the fan doesn’t work after this, you most likely have a bad fan motor that needs replacement.

A weak or dead fan motor capacitor needs a professional replacement as soon as possible. The motor it is connected to will keep trying to start up but won’t be able to on its own without the capacitor’s extra juice. The fan will then stall out, causing the motor to burn out. A new capacitor will get your air conditioner back up and running, which is vital in Arizona.

We don’t recommend trying to replace a bad capacitor yourself. For safety reasons, have a professional replace your broken capacitor. A certified and licensed technician has the proper tools, training, and experience to replace your air conditioner’s electrical components safely.

Get your AC running properly by contacting George Brazil HVAC at (602) 842-0009 or by clicking the button below. Phoenix homeowners trust our efficient and reliable same-day AC repairs.

We have thousands of 5-star reviews backing up our technical workmanship, red-carpet customer service, and speedy turnarounds. During your diagnostic, we’ll provide you with repair options and upfront pricing so that you’ll never be surprised by your final bill. Then, we’ll get to work repairing your air conditioner so that you can enjoy whole-home comfort again.