Why Is My AC Making a Humming Noise?

AC humming noises could be a symptom of a bigger problem. Noisy AC units might need maintenance, or dirty fan blades or filters may be the cause of annoying hums. These issues and several others are common. Luckily, there are plenty of tips to help you get cool and comfortable again.

In this blog, we’ll cover:

• Common causes of humming noises in AC units
• When to be concerned about a humming noise
• Steps to troubleshoot a humming AC unit
• Preventing AC noises with regular maintenance
• Ensuring long-term performance

Keep reading to discover solutions for an AC that’s making humming noises.

These are some of the common reasons for an AC unit making a humming noise:

• Loose components. Normal vibration from everyday use can cause screws, panels, or fan blades to come loose. That internal rattling can sound like humming until components are tightened and realigned.
• Electrical issues. Malfunctioning electrical components, such as relays and capacitors, can emit a humming noise.
• Blocked fan motor. A fan motor that can’t run smoothly due to dust or debris may be noisier than usual.
• Refrigerant issues. Your AC’s compressor requires refrigerant to run smoothly. Low refrigerant levels cause compressor strain, making it work harder, which leads to humming or buzzing.
• Compressor malfunction. A compressor failing due to age or general malfunction could make unusual noises.

It’s normal for air conditioners to make some noise. Sometimes, the best way to determine which noises are problematic is to assess the system to determine what other issues may be occurring.

You may have a problem if:

• The household AC unit hums but does not turn on
• The air conditioner fan is not spinning but hums
• Humming is accompanied by issues such as reduced cooling, increased humidity, or repeated system cycling
• There are odd odors present, like the smell of something burning or an unusual chemical aroma

Troubleshoot an AC unit that’s humming using these steps:

• Check the air filter. Air filters must be clean and in good condition to allow proper airflow. Clean or replace as needed.
• Inspect the outdoor unit. Clear away any leaves, dirt, or debris blocking airflow outdoors.
• Listen closely to isolate the sound. Find the source of the humming — it could be the fan, the compressor, or other components.
• Check the circuit breaker. Look for a tripped breaker and reset it if needed.
• Avoid DIY repairs for electrical or refrigerant issues. Call a licensed HVAC professional for any electrical repairs beyond resetting the breaker and for all refrigerant issues.

Regular maintenance can help prevent problems from occurring long before your inside unit starts making a humming noise. Take preventative steps such as:

• Committing to two tune-ups per year. Your HVAC technician will inspect and tighten components, clean your AC’s coils, and test the electrical connections.
• Regularly replace air filters. This helps maintain proper airflow and reduce strain on your system.
• Schedule a professional inspection. Some noises require an expert assessment, especially if your initial troubleshooting doesn’t yield easy-to-fix results.