Everyone’s AC makes noise. The fan and the compressor both produce sound while they’re running. But not all AC noises are created equal. If your air conditioner is making a whistling noise inside your house then something is wrong with your AC unit. In this blog, we’ll cover air filter whistling noise, air flow whistling noise, and other sounds which signify something is wrong with your AC unit.
Dirty Duct Ditties
You know the expression, “clean as a whistle?” Well, if your AC is whistling, then most likely it isn’t clean. When you purse your lips to whistle, you’re limiting the airflow to create a shrill note. The same principle applies to a referee’s whistle in a football game. The ref blows air into the whistle, but the air gets backed up and caught inside the whistle’s body. The air bounces around, looking for an exit, and finally escapes. But because the air is so compressed, it escapes as a high-pitched note.
Ok, but what does that have to do with an AC unit? Well, there’s a chance your air filter is mimicking the focusing function of the ref’s whistle. If your air conditioner is making a whistling noise inside your house, take a look at your filter. As your AC unit’s fan pulls air into the unit to cool down, if there is enough debris in the filter, the air is forced through a narrow opening. In that way, the air filter makes a whistling noise. If you think your air filter is making a whistle noise, stop using the unit and clean (or if disposable, replace) your filter. Your AC unit works way more efficiently—and quietly—with a clean filter.
But the filter isn’t the only part of the unit that whistles when clogged. Your AC releases cool air through vents positioned around the body of the unit. If those vents are clogged, you can hear more shrill whistling. A dirty air filter’s whistling noise comes from the air in your home; a dirty vent’s whistling noise comes from the air inside your AC unit. In both instances, the whistling is a sign that the unit is wasting energy and inefficiently cooling your home. For split system air conditioners, whistling can indicate a blockage in the ducts or room vents. Anywhere air flows can potentially turn into a whistle with enough backup. The larger your AC system, the more possible clog locations.
It’s important to remember that dirt and other debris aren’t the only potential clogs in your cooling system. Window curtains, household plants and even random pieces of paper can get sucked up into your AC unit’s cooling network. But whether it is blocked vents or a clogged air filter that is making the whistling noise, you’ll want to clear the clog as soon as possible.
Melody of Mismatched Mechanisms
This issue only occurs in older, split system air conditioner units, but it’s definitely something to check if your air conditioner is making a whistling noise inside the house. As parts of a split system AC break down, it’s not uncommon for technicians to repair the failing parts. For example, if a duct corrodes and starts leaking air, there’s usually no need to replace the entire AC. However, mismatching ducts or other components of a split system AC can leave gaps in the circuit or insulation. And these gaps provide the perfect opportunity for your air conditioner to start whistling.
Misaligned ducts are another, similar problem. Earthquakes or even some heavy winds can shake a home enough to knock ductwork out of alignment. When this happens, there’s a chance to create whistle conditions, as the ducts no longer feed cleanly into each other. After a severe weather event, it’s a good idea to check your HVAC system to ensure that everything is still running correctly and the airflow through the system remains unobstructed.
When considering the circuit in your AC system, remember that it’s larger than just your AC unit and the ducts. Every door in your home impacts the airflow through your AC system. So if you hear a faint whistling noise, it could be that the doors are blocking off airflow to intake vents, creating a whistle effect as the AC tries to draw in more air to cool.
Compromised Compressor Concertos
If you’ve read a lot of our blogs on AC maintenance and troubleshooting, you might suspect the compressor is the source of that irritating whistling. And while we never want to say never—we’ve seen a lot of different AC situations—it’s pretty unlikely that your AC compressor makes a whistling noise.
As we’ve explained, airflow is necessary to create a whistling sound, and air doesn’t really flow through your compressor. But let’s say you’re confident your AC compressor is making a whistling noise; what could that mean? Well, the compressor works by applying pressure and heat to the refrigerant in your AC unit, which turns the refrigerant into a gas. If your AC compressor is making a whistling noise, that would mean there is a leak somewhere in the refrigerant line so that either air is getting in, or pressurized refrigerant is leaking out.
As we said previously, this is extremely uncommon and would only occur in a rare situation where your AC took a lot of physical contact. We’re bringing it up because many customers know about the dangers refrigerants can pose, and are worried about possible refrigerant leaks. If you have reason to suspect your refrigerant is leaking, stop using your air conditioner immediately. If, for example, you hear whistling and then your AC shuts itself off, it’s possible that your unit detected a refrigerant leak. So the good news is that your AC’s sensors worked correctly, but the bad news is that you wouldn’t be able to use the AC until the refrigerant leak is resolved.
Again, refrigerant leaks are uncommon and are accompanied by many warning signs beyond just a whistling sound. You shouldn’t assume there is an issue with your AC compressor If you hear a whistling noise.
Additional Acoustic Antagonism
Okay, but let’s say you aren’t hearing a whistle. What about grinding noises? Or whining noises? Or what about the dreaded splash? It can be difficult to convey a sound in words, but we’ll briefly go over some places to check when you hear different, troubling noises.
Scratching: This is a sign that the internal mechanics aren’t running smoothly. The fan might be off its axle, for example.
Grinding: Another sign there’s an issue with the internal mechanism. The fan could be running into some sort of interference as it spins, or the compressor could be misaligned.
Banging: Usually a sign that an internal component is loose. Over time, parts of the AC unit wear down, and could potentially come loose.
Buzzing: Buzzing can be caused by debris loose inside your AC unit.
Clicking: Clicking can be caused by a rotational issue with your fan, an electrical issue sending faulty signals, or a power issue causing electrical failure.
Rattling: Rattling could be a sign that your AC unit is about to give up the ghost. However, rattling can also come from debris loose inside the unit.
Splashing: If you hear splashing, that means part of the unit’s mechanism (most often the fan) is hitting moisture that has collected within the unit. This means there’s an issue with your unit’s drainage.
If you hear any unexpected sound from your AC unit, it’s a sign that something is wrong. We’ve gone in-depth on what could be wrong when your air conditioner is making a whistling noise inside your house, and the differences between air filter whistling noises and other types of whistling noises, and what other troubling sounds might signify.
If your air conditioner is making a whistling noise inside the house, try to resolve the issue before resuming operation. Many of these issues, if exacerbated, can cause larger problems for your air conditioning system. If you have more questions or need help troubleshooting, our support team is available seven days a week to assist you.