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27 Apr 2023

HVAC systems comprise several components, and most of them, based on their design, generate a good deal of noise. Blower motors and fans are noisy, as are furnaces and outdoor air conditioning units that contain the system’s compressor and cooling fan. So, a certain amount of noise is expected when running a complex mechanical device like a furnace or air conditioner. The noises become so familiar that we eventually neglect to notice when the HVAC system turns on and runs its cycle. 

But what about new sounds? What about sounds that you know you should never hear coming from a central HVAC system? Most of the time, we’ll notice these new noises when we turn our air conditioner on for the first hot day of the season after a few months of inactivity.

This Nick’s Air Conditioning blog may not turn you into an Air Conditioner Whisperer, but it will teach you how to recognize the odd noises from your AC system and what each could be telling you.

Common HVAC Noises That Could Mean Trouble!

Banging Sounds. 

Any loud banging sounds, particularly when the unit starts up, indicate that something in the system is loose. If the sound comes from the outdoor unit, your compressor may have worked itself loose or could have a faulty bearing that requires service. 

Banging or rattling sounds coming from your ductwork while the system is running could mean sections of your ducts have worked themselves loose. 

Buzzing Noises.

Buzzing, humming, or intermittent popping is almost always (99.99% of the time) related to an electrical issue and requires the intervention of a professional HVAC company. No good can come from any homeowner getting involved with loose wiring, leaking capacitors, or sputtering motors. HVAC systems are not powered by standard 110-volt wiring, with most systems running at 240 volts, with larger, more complex systems requiring a 480-volt supply.

The most you’ll want to do in this situation is to locate where the hum or buzz originates. If your HVAC is in the attic, go upstairs, and if the buzzing gets louder, you probably have a faulty blower fan motor. Remember that loose wiring or faulty connections and electrical components can also emit a buzzing sound, so avoid contacting the HVAC unit. 

Clicking Sounds.

HVAC systems and their various functions are controlled by an array of electrical switches, relays, and other mechanical parts that make noise when in use. Most homeowners eventually get used to the various sounds of regular HVAC operation and rarely pay them a second thought. It’s only when unusual sounds emit from the HVAC equipment that we take notice. 

If your thermostat is making clicking noises, and nothing is happening with your AC system, the wiring to the thermostat could be an issue, or it could be as simple as needing to replace the thermostat. 

Clicking sounds coming from the outdoor AC unit usually indicate an electrical problem, such as a faulty relay switch or a capacitor that has gone bad. Both issues will cause the components to “click” as the relay switch engages but will fail to power up the compressor to run the AC system. 

Squealing –or “Metal on Metal”—Sounds.

Nope. That awful, grating, unending cacophony of noise is not your son blasting the latest Metallica album; it’s probably your air conditioning compressor telling you it’s about to give up. AC compressors use ball bearings to make it possible to reach the rotational speed necessary to pressurize liquid refrigerant into a chilled gas.

As we’ve mentioned earlier, the compressor is literally the heart of any air conditioning system; without it, the rest of the system is useless. Over years of use, the tightly packed ball bearings begin to flatten on the side that contacts the motor drive. Once the bearings have become misshapen, the lubricant that keeps the bearing moving smoothly can escape and evaporate. 

The same condition can occur with your indoor blower motor fan, where bearings, age, and lack of lubrication allow that screeching sound to occur. It almost sounds like your HVAC is in pain, and in a way, it is suffering. 

Strange Smells Associated with AC Noises.

When metal rubs on metal at the high rate of speed required for AC compressors and blower fan motors, it will smell like hot metal. Unfortunately, since the AC compressor unit is outdoors, it may be difficult to detect odors around it. Blower motor fans, being located indoors, are more likely to alert you to a worn bearing issue with the associated sounds and the metal-on-metal odor. 

Short Cycling.

A short cycling air conditioner may make various noises, depending on the specific cause of the short cycling. If the unit is short cycling due to a dirty or clogged air filter, it may produce a whistling or hissing sound as the air struggles to pass through the filter.

If the thermostat is malfunctioning and causing the unit to turn on and off too frequently, it may produce a clicking or snapping sound as it switches the system on and off. If the compressor is

short cycling, it may produce a loud humming or buzzing noise as it struggles to start and then quickly shut off.

What Can I Do If My HVAC System is Crying Out for Help?

The sounds we’ve listed above are signs of potentially serious issues with your HVAC system. It’s essential that you have a professional HVAC technician diagnose and repair them, as attempting to fix the problem yourself could lead to further damage to the unit or even personal injury. 

Preventative Maintenance Could Prevent These Problems!

Regular AC maintenance and tune-ups can also help prevent these issues from occurring in the first place. Annual HVAC system inspections can catch many problems before they can affect your unit’s performance. 

Call Houston’s Top HVAC Company When Your AC Noises Keep You Up at Night.

Nick’s Air Conditioning is well-versed in our heating and air conditioning systems’ language. Our licensed, experienced, and thoroughly background-checked HVAC technical crew knows how to listen to the complaints of your system, interpret them, and solve the problem. Regardless of the make or model of your HVAC equipment, our techs know how to eliminate disturbing noises in any home comfort system. 

If you’re hearing concerning sounds starting to come from any of your heating or air conditioning equipment, remember “time = damage,” and call Nick’s Air Conditioning immediately. From simple repairs, complex compressor replacements, annual system maintenance, or complete HVAC system replacement. Find out why Nick’s is Houston’s best choice to quickly get your home back into its comfort zone. 

Call Nick’s Today. We’re on the Way!

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