AC Noises: How to Fix Grinding & Whistling

It goes without saying that your AC unit is going to make some noise as it runs. Any fully operational machinery does. However, there are some types of noises you don’t want to hear from your air conditioner, some of which are a clear indicator that a problem has occurred within your unit.

If you hear your air conditioner making a high-pitched whistle noise or a grinding sound, here’s how you fix it.

What Does It Mean When Your Air Conditioner Whistles?

While an air conditioner making a high-pitched whistle could be completely benign, that whistling or hissing sound could also be a sign of a few different maintenance issues such as a dirty air filter, blocked vents, a refrigerant leak, or high air pressure in the compressor.

If the air conditioner whistle is persistent, consider the following potential issues and how to solve them.

Dirty Air Filter

If you hear a whistling sound coming through your air vents, one of the easiest steps is to replace your current air filter with a new, clean one. As air filters fill up with contaminants and unwanted particles from the air, they restrict airflow and could cause a whistling sound.

Blocked Vents

An air conditioner making a high-pitched whistle sound could be due to blocked air vents. Double-check yours to be sure they’re all open and allowing air to flow freely.

A Refrigerant Leak

A refrigerant leak can occur either in your AC unit’s internal valve or the refrigerant lines. This often causes your air conditioner to make a high-pitched whistle, hissing, or bubbling sound. This issue should be investigated immediately and addressed as soon as possible since a leaky internal valve or damaged refrigerant lines worsen the longer they’re left unchecked. Be sure to turn your air conditioner off when inspecting for a leak. 

For your AC unit to run properly, the refrigerant levels must be precise so to fix this issue, you’ll need a licensed professional HVAC technician. Find a trustworthy HVAC technician to correct the refrigerant levels and fix a refrigerant leak in your unit, and it’ll be up and running before you know it.

High Air Pressure in the Compressor

Another reason your air conditioner is making a high-pitched whistle could be due to the pressure inside your air compressor. If the pressure is too high, whistling or hissing sounds can intensify to a high-pitched screaming sound. Hissing, whistling, or shrieking coming from your compressor is a sign the air pressure is too high.

To resolve this issue, turn off your air conditioner the moment you realize the sounds are coming from your compressor. Leaving it on could damage your unit further. Leave your AC unit off until you can have a technician come to investigate. 

What Causes Your Ac Compressor To Make A Grinding Noise?

Regardless of what kind of mechanical object it is, a metal-against-metal grinding noise is never a promising sound. This is especially true for an AC unit. If you hear your AC compressor making a grinding noise, here’s what could be going on.

Compressor Issues

This is the most common cause of grinding noises in an AC unit. An AC compressor can make a grinding noise when it’s turned off, or while it runs.

The compressor is a vital component to your AC unit, and the grinding noise it makes is from pistons that compress refrigerant gas. This grinding typically only happens when the compressor is old and worn down, meaning it needs to be replaced when the grinding begins (which often means your whole air conditioning unit needs to be replaced since the compressor is such an integral part).

If your AC compressor makes a grinding noise when off or while your AC unit is running, stop running it immediately and schedule an appointment with your HVAC technician to get the issue checked.

Damaged Belts

To cool your home, your air conditioner uses a blower fan to move air. The motor fan has a belt to help it turn. If this belt gets damaged or is loosened in any way, it rubs against other parts of your air conditioner, resulting in a grinding noise. If left unresolved, a damaged or loose motor belt can cause more issues for other portions of your air conditioner. Replacing it as soon as possible is best for the health of your unit.

Lack of Lubrication

Your AC unit is a machine with a motor, and like most motors, it requires the right amount of lubrication to run optimally. Many older AC units (and some newer ones that are well used) need more lubrication or they’ll begin grinding. To help your AC unit run smoothly and quietly, and to help protect it from damage, have an HVAC specialist ensure the motor is properly lubricated.

Don’t Wait for the Noises to Go Away – Fix Them!

Since unresolved AC maintenance issues tend to cause more damage the longer they’re left unattended, never let unusual noises go unchecked. Resolve them as soon as possible. Are you experiencing weird noises coming from your AC? If your AC compressor makes grinding noises when it’s turned off, call 703-214-5611 or contact the John C. Flood certified HVAC technicians online now.

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