Do you hear a grating, high-pitched whistle coming from your vents? If so, it’s probably driving you crazy.
Here’s why you’re hearing that sound: Your A/C system has low return airflow, which means it isn’t getting enough air through its return vents.
Many problems can cause low return airflow, but here are 4 of the most common:
We’ll go over these problems in more detail and discuss what you can do to fix them. But first, let’s look at how low airflow causes your air conditioning system to produce that whistling sound:
An A/C blower pulling in air from the home.
Your air conditioner's blower constantly circulates air in your home. But if your blower isn’t receiving enough air to circulate because something’s blocking or restricting airflow (like the problems we discuss in the next section), then it’s essentially “starved for air.”
If your system is “starved for air,” it means there’s more pressure and velocity, which means you’ll hear a louder and higher sound.
Think of it like whistling compared to normal breathing: When you whistle, you must pucker and tighten your lips to create a small passageway for the air to pass through, which makes the high-pitched sound. But when you’re breathing normally, your mouth is wide and open and the air you exhale silently.
While that whistling sound can be annoying, the good thing is that it alerts you of a problem in your system. Low airflow can damage your system and raise your energy bills, so you’ll want to fix whatever’s causing the problem ASAP.
Now let’s go into the specifics of each airflow problem...
If your filter looks like the one on the right, it’s dirty and you should change it.
Similar to using a strainer while cooking, your air filters pick out unwanted contaminants from your home’s air. But when the filters get too dirty, they restrict airflow and can cause overheating problems.
Solution: Change your air filters every 3 months at a minimum, and preferably every month during the summer.
A return vent in a stairwell.
Your return vents are large vents that are usually located in a hallway, staircase or open area. If something is blocking them, like furniture or heavy dust or debris, then your system isn’t getting enough air.
A supply vent.
Your supply vents are the grates with levers that actually provide air to your home. If these are closed or blocked by furniture, your system is going to have low airflow.
Solution: Clean the return vent grill and remove any furniture that may be blocking airflow. Make sure your supply vents are all open (even in rooms you don’t use).
Dampers are metal valves in your ductwork that you can shut to prevent air from being delivered to certain parts of your home.
Solution: Locate the damper levers near your inside unit and make sure they’re aligned with the ductwork to allow airflow.
If too many doors are closed in your home, then the supply air has to sneak under the small gaps under the door to the return vents (usually located in a hallway or stairway). This makes your blower work even harder to pull in more air, which causes the whistling noise.
Solution: When possible, keep your doors open to allow proper airflow.
Try all these DIY repairs, but if those don't solve the problem, it’s time to call a professional...
The airflow problems we just covered can be solved by any homeowner. However, sometimes that whistling sound is caused by bigger problems that only a certified AC contractor can properly fix.
These include airflow problems like…
Contact Cool Today for an air conditioning repair estimate. We’ll send one of our trusted technicians to your home to diagnose the problem and give you an honest repair quote.
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Posted in: Troubleshooting