Have you ever woken up to the sound of a furnace making a high-pitched whining noise? It’s one of the most frustrating things about owning an HVAC system. While a furnace makes lots of noises, it shouldn’t make strange high-pitched sounds.
Common reasons for a furnace making a whining noise range from being relatively harmless, such as loose belts, to much more dire issues involving the heat exchanger or blower motor.
This guide covers why a furnace makes a whining noise and provides easy fixes to common causes of this problem. Let’s get started!
Bad Blower Motor Bearing
Whining noise in most cases is due to a bad motor bearing. A bad motor bearing will result in excessive vibration which may travel outside the furnace through various ducts. You may be able to identify the bad bearing by operating your furnace with no load.
A good bearing will allow the blower wheel to spin freely and quietly. If, on the other hand, you find that a blower wheel is noisy and has excessive vibration when operated with no load, you likely have a bad motor bearing. Replace your blower assembly if you suspect it has a bad bearing.
How to Fix
1. Disassemble the motor.
2. Remove the bearing. Be careful during this process so you don’t lose the bearings.
3. Buy similar replacement bearings.
4. Heat up and mount the new bearing. When heating, use an induction heater till a warmth of 20–50°C (70–120°F) is attained.
Fixing the blower motor bearing motor can be quite tricky, so here’s a video that shows you how it’s done:
If your hot air furnace is making a whining noise, the most likely cause is from the burners. If they’re not cleaned regularly, the heat and flames can warp the metal chamber that the burners come in contact with.
This can make them stick, so when you press on them to light or start a fire, they tend to make a whiny noise. Turn off the furnace and then try to turn on the gas valve by hand. If you hear nothing but silence, then it means the burners are dirty and need to be cleaned.
If your burners are dirty, they may be reducing the flames’ ability to heat the firebox. This will make it whistle to try and draw in more oxygen.
When you clean the burners, stir up or scrape out any ash from the ashes to free up any trapped deposits and optimize the heat transfer through the tubes.
How to Fix
1. Turn off the furnace if it is currently running.
2. Inspect to see if the burner is dirty or release pressure. Do this by shining a light over the burners.
3. If any of them show signs of blockage or burning debris, use a grease-cutting detergent to clean thoroughly with an old toothbrush.
4. Rinse with a rag.
5. Make sure to be gentle about the process so that you do not damage the burner.
Learn how to properly clean a dirty burner by watching this video:
Broken Blower Wheel
If your home’s furnace is making a whining noise, the first thing you should check is if it’s caused by a broken blower wheel. Blower wheels are responsible for moving cool air through the ducts and into your rooms.
A broken blower wheel causes bad circulation in the furnace and could increase its energy consumption because of increased power costs to produce more airflow, which makes an extremely high-pitched shrieking sound.
How to Fix
1. Turn your furnace off at the breaker, and let it cool down before you proceed.
2. Your furnace has a panel that covers some of the ports. Remove the panel to gain access to those ports.
3. Carefully dismantle the wheels
4. Get your replacement blower wheel ready.
5. Fixed the blower wheel couple up the parts.
It’s is advisable to call an HVAC specialist. It saves you time and you can rest assured that your broken blower wheel will be fixed.
For more information on how to replace a broken blower wheel, watch this video on HVAC with John Isreal
Unlubricated Shaft Bearings
One of the most common causes of a furnace whining noise is that the bearings that support the motor shaft pinion gear need lubrication. The bearings allow the motor to spin freely while supporting the shaft on both ends.
There are two bearings, which both require lubrication. If you notice your furnace start making a lot of noise when it first comes on, this is an indication that you either need to clean or lubricate the bearings.
When the bearings have been well lubricated and they spin freely, it’s easier to operate and it won’t make as much noise.
How to Fix
1. Clean the shaft bearing by removing any existing oils, anti-corrosion coatings, and grease with a paint stripping product.
2. Add a few drops of lightweight oil to the lubrication port at each end of the shaft.
3. If this doesn’t work or if you, contact an HVAC specialist for further assistance.
Watch the video below to see how to properly lubricate bearings.
Loose or Fraying Blower Belt
The most common cause of a furnace making a whining noise is a loose or fraying blower belt. The blower belt is responsible for spinning the motor that pushes air throughout your house, which helps heat it.
If the belt is loose or frayed, it might slip through the pulleys on the blower motor and cause the loud whining sound as the belt continues to spin itself in circles. Before calling in a technician though, try tightening or replacing the belt by following these steps:
How to Fix
1. Check to see if you have a loose belt or general wear and tear.
2. Confirm if there is no slack on the belt
3. If you notice a slack, tighten it by using a motor adjusting belt. Remember not to tighten too much as that may lead to other serious problems.
4. Make sure the pulley is properly lined up.
5. Install the belt
For a detailed video on how to repair and replace a blower belt, check on this video from repair and replace by Vance.
Malfunctioning Blower Motor
A furnace blower motor is a necessary part of your heating system and keeps the air moving through your whole home. If your furnace is making a whining noise, the most likely cause is a malfunctioning blower motor, which is in charge of delivering air through the ductwork.
If the problem is caused by a malfunctioning blower wheel, you’ll need to replace it—no do-it-yourself fixes here. If you have access to an HVAC specialist, contact them and request a troubleshoot of the problem.
When you call, be sure to tell the specialist what series of furnaces you have and what motor model you need.
To learn how to troubleshoot your blower motor, watch this video:
How to Fix
This is a complicated repair, so I highly recommend you call an HVAC repair specialist.
Here is a video that shows you how to troubleshoot a furnace blower motor.