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What's That Noise?!

After years in your home, you may have become immune to all of the many sounds – gurgling and whirring of the washing machine, the ice dropping in the freezer, the clicking of your teenager speed-texting, the young ones arguing over the XBox….. You may even ignore the sounds of your heating and air conditioning system.

No matter how old your heating system is, it is going to make some noise. However, there are some HVAC-related sounds that you shouldn’t overlook. It is important that you can determine what is normal and what is not in order to identify the source.


When your thermostat calls for heat, it signals for the system to turn on. You’ll know this is happening because there will be a clicking sound at the thermostat. If you hear this while the system is running or multiple times within a short period, you may have an issue causing the system to short-cycle.


The blower motor and fan blades may cause a quiet hum while you’re system is running. You may also hear of air whooshing through your vents. This will happen during normal operation.


You may hear the sound of air whooshing through your ductwork and vents while it is running. This is also normal. A hissing noise, however, could be a sign of leaking or obstructed ductwork. Either of these can cause your system to run more frequently, cost more to operate, and eventually cause system failure. If the ducts in the attic or crawl are leaking, it could cause poor air quality in the home. If you hear the hissing at the return air grill, make sure that your air filter is the correct size and that it is installed incorrectly.


Thumping or popping sound could be caused by your metal ductwork expanding and contracting when it is heated or cooled. This is normal. If it is annoying to you, a Technician can offer solutions to lessen the noise.


If you hear a boom or bang, it may be due to a small gas explosion because of a delayed ignition. Gas can build up in the furnace chamber and “explode” when the furnace finally ignites. You can best protect your system with an immediate call to Helms to diagnose the potential problem:

  • Delayed ignition. Gas can build up in the furnace chamber and “explode” when the furnace finally ignites. Your system could be not getting enough gas or have an issue with worn or clogged burners. A Technician can check and adjust the gas pressures, clean the burners, and/or diagnose and replace a faulty regulator or gas valve.

  • A bang or rattling sound coming from your furnace when it first kicks on could mean you have a cracked heat exchanger, which is the biggest cause of carbon monoxide leaks.


If you are hearing clanking or rattling, turn the system off immediately and call for a Technician.

  • Your blower wheel/fan may have come loose and is hitting the blower housing. If it isn’t damaged, the repair should be quick and easy.

  • A part could have broken or come loose and is stuck in the blower wheel.

  • Parts can become loose or unaligned overtime because of the vibration during operation. These problems should be addressed before the part breaks or disconnects completely.


If you hear a squealing or screeching noise at your furnace, your blower motor may be malfunctioning. It is best to have it resolved immediately as it could lead to an expensive repair.


If your furnace is rumbling, it usually indicates that it has not been maintained in a while. There could be soot or dirt buildup on your gas burners or pilot.


If you are hearing a whistling or suction sound at your return air grill, it could caused by the lack of return air. This could be caused by:

  • Blocked Vents – Make sure you don’t have too many vents closed off or anything (furniture, drapes, etc.) blocking your vents

  • Dirty Filter - replace your filter

  • Debris – you may have debris or a rodent that has infiltrated your ducts. Call to have your ductwork inspected.

  • Undersized, Restricted, or Damaged Ducts – Call to have your ductwork inspected.

Helms Heating & Air Conditioning Technicians are equipped to locate and eliminate any strange noises and potential failures. They can also provide regular maintenance to keep your furnace quiet, running properly, and prolong its lifespan.



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