Reasons Your Furnace Makes a Loud Noise | Mission Air Conditioning

Why Is My Furnace Making a Loud Noise?

Usually, homeowners don’t give their air conditioner or furnace much thought as long as they're working correctly. It's not until there's banging or another loud noise coming from the vicinity of the HVAC system that you start to pay attention. At Mission Air Conditioning, we not only want to offer professional heating repair in Houston, we also want to educate our customers on their HVAC system. Here, we'd like to take a moment to discuss why your furnace makes a loud noise


Vibrating and Rattling

If you happen to hear rattling or vibrating coming from your ducts or the furnace itself, you can easily take care of the problem yourself without having to call a professional. First, you'll want to inspect your ducts to see if they're loose, tightening or adding screws as necessary. You can also use duct tape to keep ducts from rattling loose. There's also a chance you might need to add cork or rubber pads underneath your furnace.



The sound of whistling coming from your furnace might indicate there's a gap in your ducts or too much air pressure. Before remedying the situation, try your best to determine exactly where the noise is coming from. The reason for the whistling sound could be that your furnace filter has become clogged. Pulling out your filter and listening to see if the noise stops after doing so is a solid way to determine for sure whether it's a clogged filter that's causing the noise. If it's time to replace or clean your filter, it might also be time for heating repair in Houston, so be sure to have your unit inspected. 


Banging When the Furnace Is First Turned On

When you turn your furnace on and hear banging, there are two potential problems. The first is that the structure of your ducts is compromised and needs a piece of metal that's a bit thicker than the ducts to be screwed across and onto the part that's weakened. This is called "oil-canning ductwork." 

There's also a chance that there's a small explosion that's causing the banging sound, something called "ignition roll-out." To see if this is the source of the sound, pay close attention to your furnace and have someone start it up. Either look inside the furnace doors or listen as the unit starts up. Any shaking or extra burst of flame should be inspected by a licensed HVAC technician as soon as possible.


The Sound of Metal on Metal

Does your furnace sound more like metal scraping metal or nails on a chalkboard? If so, the problem is likely focused on the blower wheel inside your furnace. You'll want to shut off your unit immediately if you hear this sound and contact a heater repair specialist to come take a look at your furnace. 

There are a few things that might have happened to trigger the scraping sound:

  • The motor mount failed, which caused the entire blower assembly or wheel to come into contact with the furnace housing. 
  • The blower wheel loosened from the motor shaft and is knocking against the blower casing. 
  • The blower wheel is simply in need of replacing. 


Banging or Popping When the Furnace Switches On

A furnace that sounds more like a garage band warming up likely has one of two issues, possibly both. Your metal ducts might be expanding and contracting, which is often due to them being too small or made of poor quality. You might also need to clean your furnace burners. Dirt on furnace burners keeps them from igniting as they should, which leads to a block in the flow of gas. When the gas is finally able to burn as it should, it does so with a bang. In both cases, you'll want to get in touch with one of our technicians to come take a look at your unit to develop a solution. 


High-Pitched Squealing

A malfunctioning inducer draft motor or blower wheel is often the reason for any squealing or whining you hear from your furnace. There's also a chance your unit's shaft bearings need to be oiled up to smooth out their performance. Finally, you may need to simply replace or fix your blower or inducer motor. 

One thing to note with a squealing furnace is that it's not one of the more serious furnace issues, meaning you don't have to arrange for emergency repair services. That being said, you do want to have the issue taken care of sooner rather than later to keep from experiencing other issues that could lead to you spending more money than necessary. 


Clicking or Rattling Noises

Hearing a rattling or tapping noise coming from your furnace?  A common cause is paper or debris caught in the blower wheel.  Removing the paper or debris can often solve the tapping noise. Be sure to have the unit powered off before removing anything caught in the blower.

If it's a clicking noise you hear from your furnace, the culprit is likely the ignition system. The noise is the result of the spark igniter attempting and failing to trigger the pilot light, which also causes your furnace not to work properly. To narrow down the true reason behind the clicking noise, light the pilot to see if it sparks. 

If it's rattling you hear instead of clicking, something could be coming loose inside your furnace. Unlike high-pitched squealing noises, rattling is an issue that needs to be attended to ASAP. You might need a repair or replacement before your furnace is able to operate normally again. 


Reasons to Keep Your Furnace in Good Shape

Once you take care of the loud noise coming from your furnace, be sure to keep up with regular HVAC maintenance throughout the year to keep from hearing odd noises in the future. We understand that you might not want to spend extra money on upkeep, but doing so actually saves you money in the long run. Additional reasons to properly maintain your furnace include:

  • Extending the overall life of your unit, which means not having to buy a new one sooner than necessary
  • Making your home safer, healthier and more comfortable, because the condition of your unit plays a huge part in the overall quality of your home's air
  • Lowering the chances of your unit breaking down unexpectedly
  • Keeping your energy costs and heating bills as low as possible

If you'd like, we'd be more than happy to work with you to figure out a solid maintenance schedule for your HVAC unit. The age of your unit, how often you use it and the general condition of your unit are just three factors that determine how often it should be serviced by a professional. 

The next time you hear a loud or odd noise coming from your furnace, be sure to call Mission Air Conditioning. We're here to keep your unit fully operational, quiet and performing at its best all year round.