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Why Your AC is Making a Noise

If your AC is making a noise, it can quickly become concerning. Screeching, grinding, clanging and banging are not normal sounds you should hear coming from your heating and air system. AC noises can cause a panic. However, often times these are signs that there is a problem occurring and needs immediate attention before the problem causes major damage to your system. If addressed in an appropriate time, you may be able to prevent more costly repairs such as replacing a compressor or fan motor. Review the list of noises our heating and air experts come across:

Banging and Rattling AC

  • Debris Lodged In Your Outdoor Unit- Sometimes leaves, sticks, or twigs can become lodged in your system. This can cause rattling and clanging. Make sure any shrubbery is trimmed back and at least 3 feet away from your outdoor unit. Upon visual inspection, if you see much debris inside your unit, you can remove the outer cover and attempt to remove it. It is recommended that you have a seasonal heating and air tune up to check the system components fully and clean your unit.
  • Loose Screws and Connections- Your outdoor unit will vibrate which can loosen connections and screws. If you are hearing a rattling or pinging noise, the screws may just need some tightening. Often times, screws may come undone causing panels to vibrate. A visual check will allow you to see if this is the case. Replacing the screws may solve the noise problem but, it is always a good idea to verify your system is in working order with a seasonal tune up.
  • Malfunctioning AC Fan Motor or Broken Compressor- A banging noise upon start up is a possible sign of a malfunctioning compressor. Often this can be a costly repair with an intact warranty or not. Evaluating the age of your system, cost for repair, and cost for replacement is a great place to start. Repairing an aging system that is out of warranty may not provide you as much of a benefit as replacement. A broken or off balance fan motor can cause clanging from your inside unit. This too is a costly repair and should be evaluated for a repair or replacement cost benefit. Learn more about repair or replace benefits here.

Extended the longevity of your system and breakdown prevention can be easily rectified with routine heating and air maintenance.

Hissing Sound From AC

  • Leaking Refrigerant- Hissing noises from your outdoor AC unit can be caused by a broken refrigerant line. Overtime the refrigerant lines can become damaged from weed eaters or just deterioration. This wear and tear can cause pin hole leaks that over time will enlarge. There is no quick fix or DIY for leaking refrigerant. Depending on the age of your system, you may need a leak detection test and repair. However, this can be a hefty cost due to the labor involved. It may make more sense on an aging system to consider replacement. Especially if your system uses R22 refrigerant which is now outdated and supplies are limited.
  • Valve Leak- There are valves on your compressor which control the pressurization of the refrigerant. Damage to these valves can lead to costly repairs. Contacting your trusted heating and air experts is crucial to getting this problem rectified right away.

Whistling Noise From AC

  • Air Flow Restrictions- As air is being pushed into your ducts, if there is anything that restricts the free passing of the air, you may hear a whistling or wheezing noise. We have seen filters become lodged, dirty air filters and even insulation or debris enter the ducting system that can cause your AC to make a noise and require ac repair.
  • Detached / Damaged Ducts-Improperly secured or leaking ducts can make a whistling sound. Not only are leaky ducts annoying but can drive up your energy costs and provide less air flow to associated rooms. This is an easy fix with proper duct sealing and can be quickly handled with a service expert.

Buzzing Or Grinding Sound From AC

ac making noise

  • Capacitor Breakdown- A capacitor stores energy until it is needed and then powers on to the outside unit of your AC to make it operational. If this component fails, you will generally have no cold air coming from your vents and the fan will not turn on. This can cause a buzzing sound. Turn off your unit at the thermostat. We recommend you have a professional who understands HVAC wiring install a new one.
  • Loose Wires- A constant buzzing sound may be due to exposed wiring or loose wires. This can be a hazard so we absolutely recommend you turn off your HVAC unit and contact Guardian for repair.
  • Faulty Motor- A motor that has malfunctioned can make a buzzing or grinding noise. As it attempts to work, but with potential restrictions, the motor can cease and make a low buzz or hum. It is crucial that you turn off your heating and air system and contact your favorite expert from Guardian.

While there are many more parts in your system that can fail, we have isolated the most common ac repairs. Contact the experts at Guardian today. Whether you need ac repairs in Marietta, Acworth or Sandy Springs, Guardian is your home services company of choice.


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