AC Condenser Fan

Noises you may hear when you turn on your furnace

Home » Do-It-Yourself Tips » Noises you may hear when you turn on your furnace
Posted December 15, 2018
House with scarf

A furnace is a piece of mechanical equipment – and as such, it has moving parts which make some noise when it’s in use. There are, however, differences between ‘good’ noises and ‘bad’ ones. The nice quiet hum of motors running smoothly and fans blowing, and air whooshing up through vents all count as ‘good’ or normal. However, there are strange noises which occur from time to time that may make you wonder if something has gone awry.


  • Rumbling

If you have a gas furnace, that low rumble you hear when it first kicks on is quite normal. Now if that rumble becomes louder than usual or lasts longer than usual, this could mean there’s a serious problem with your burner. In the case of loud or long rumbling, turn off your furnace right away and call for service.


  • Popping

Don’t worry if you hear popping sounds when cold weather has you turning on the furnace. Those pops are quite common, especially when your turn on your furnace at the beginning of the heating season. It generally means the sheet metal in your ductwork is responding to pressure from the heated air, popping one way in reacting to the negative air pressure of the fan blowing, then popping back out when the fan shuts off and the pressure is released. If the popping becomes loud or persistent and won’t go away, you may want to have your ducts inspected.


  • Rattling

If the fasteners to the metal housing on your heating unit have worked loose, you might hear a rattling or buzzing sound. That doesn’t usually mean anything serious, and these can easily be tightened. However, if there’s a rattling noise coming from inside your unit, it might be something more significant. It could be just a twig or some outside debris clanking around inside, but if something has caused damage to the fan or other parts, it probably warrants a call to a furnace technician.


  • Thumping

Thumping usually indicates that something is out of balance – like when your laundry load gets bunched up on one side of the washer tub. In the case of your furnace, it could mean a motor or blower wheel is out of balance. This could cause big problems for the mechanical parts in your furnace, so it’s best to have an HVAC professional check it out before a small problem becomes a big repair.


  • Scraping

Scraping is never a pleasant sound – it’s hard on the ears, and it likely means something is wrong with your fan blades or even the motor. If you hear a scraping noise coming from your furnace, the best thing to do is turn it off right away and call a technician. It’s likely that either a foreign object is obstructing your blower, or possibly one of your fan blades is broken or warped. Either way, this can lead to a motor burn out.


  • Hissing

Escaping air is usually the cause of hissing. That escaping air could be the result of an improperly installed air filter, or one that is the wrong size. Hissing can also occur if you have too many closed vents, or if there is furniture blocking air flow. If the hisses are rather loud, it could mean you have a leak in your ducts, so it’s a good idea to see if you’re letting a lot of expensively heated air escape through a hole or open seam in your ductwork.


  • Whistling

Whistling is a happy noise when people are doing the whistling – if it’s your HVAC equipment it’s a sign there might be a refrigerant leak in your condenser, or some other issue that’s causing internal pressure. Whistling noises of that sort fall into the category of “not good”. If your furnace is whistling at you – call for a service technician.


Noises aren’t always bad – and even when they’re bad, they’re a warning that something needs to be addressed. If you hear any loud, disruptive, or continual noises coming from your HVAC, schedule an inspection with a local furnace service provider like Air Specialist. They’ll be able to discover the origin of your strange noise before it becomes a huge repair or danger to your safety.


Post Categories

Resource Library
Do-It-Yourself Tips
Money Saving Tips

Why Choose Us?

  • We're strategically located in Pearland, TX
  • Expertise to service all of your HVAC equipment
  • Our technicians are NATE-certified
  • We are an ACCA member company
  • BBB accredited south Texas HVAC business
  • We stand behind all of our HVAC work