Why is my furnace making a noise, and what could it mean?

If you’ve ever heard your furnace make an unfamiliar sound such as a whistle or a knock, you might worry that it isn’t operating the way it should be. Or perhaps you’ve noticed that your furnace’s burner flame isn’t staying lit. But before you make a call to a technician, we’ve created a list of familiar sounds to help equip you with the knowledge of whether or not you can solve the problem on your own before calling in a pro.

Normal furnace sounds:

Furnaces, and their internal mechanisms, experience shifting temperature changes as they turn on and off when heating your home. These temperature changes can sometimes cause unusual sounds as metals naturally expand and contract as they heat up and cool down.

• If your furnace chirps or rattles: Chirping sounds are generally the noise of the mechanisms of the furnace working, while a subtle rattle noise at the end of a heating cycle usually indicates that the system is cooling down and motors are coasting to a stop.
  
• If you hear a hum or crackle: If you hear a humming noise and then a click at the beginning of the heating cycle, it’s usually the sound of the burner lighting, while a crackling sound typically indicates that a metal part is cooling down after a furnace has been shut off.
• If your furnace pings: A pinging noise is usually caused by contracting and expanding ducts and other metals in your furnace from normal temperature changes during and after operation.

High-efficiency furnaces capture more heat during the combustion of the gas rather than wasting it out the exhaust or chimney. This also causes condensation of the water vapors in the exhaust. If you have a high-efficiency furnace, you may hear occasional water trickling or even have a small pump that will come on and off occasionally. These sounds are also normal, but the maintenance of water tubing and pumps should be conducted regularly. If neglected, they can get clogged and cause your furnace to stop working properly.

Furnace sounds you may need a technician for:

• If you hear a loud boom or bang, instead of a ping: If the noise you hear is louder than a ping, it could still be the sound of your ductwork expanding and contracting from the change in temperature and air pressure traveling through your ducts. These sounds can change depending on how dirty your furnace filter is. The dirtier the filter the less air will pass through it which could cause different sounds in your ducts. Check your filter monthly and change it as needed. However, if you hear a boom as your furnace is starting to heat or if it produces a burning smell, you could have dirty burners or a defective gas valve, these conditions should be looked at by a technician.
• If the sound is higher than a hum or a long chirp: It could be a screech, which usually indicates a problem with your furnace’s motors. Seek immediate technician assistance.
• If you hear a whine with a strange vibrating sound: Similar to a screech, there could be a problem with your system. Contact a technician immediately.
• If you hear grinding, scraping, or rumbling noises: These can indicate motors and bearings are failing and should be serviced immediately.

Routine care improves safety, efficiency, and comfort

Minnesota's extreme seasons make maintaining your appliances a chore you can't ignore. Similar to a tune-up for your vehicle, regular tune-ups for your furnace will improve its performance and ensure it is operating the way the manufacturer intended. Routine maintenance can help give you peace of mind by identifying issues before they become a problem. To save money, avoid stress, and breathe easy, considering enrolling in a Home Service Plus Maintenance Plan or schedule an individual furnace tune-up.

If you already have an HSP maintenance plan, HSP’s Replacement Plan could help you save money on replacing your appliances. This plan applies to all appliances covered on your Basic or Total Repair Plan. If an HSP technician deems that your furnace is beyond repair, the Replacement Plan will provide a fixed payment when you purchase a new unit. Enroll in the Replacement Plan today!