How to Fix a Noisy Furnace Power Vent

Man working on a furnace
  • 1-3 hours
  • Intermediate
  • 0-100
What You'll Need
Dry rag
Sewing machine oil
New fan belt

When you’re dealing with a noisy furnace power vent, it may help a little to first understand what the vent does. If your central heating system has a furnace that’s powered by gas, the resulting oil which heats things up needs to be exhausted from the unit. To accomplish this, there is a power vent with a fan that serves to release the exhaust, and the fan continuously runs as the furnace is running.

The fan will also sometimes run if the furnace is off as well because with gas heat, you’ll always have the pilot light on. The fan part of the vent may be part of a self-contained unit near the motor or connected directly to the motor itself. When the power vent is noisy, there are a few things that could cause this.

Step 1 - Clean the Dirt on the Fan

Since the fan is moving quickly and quite frequently, there tends to be a lot of buildup of dirt and dust. When you also get humidity and condensation, all of that dirt and dust can very quickly turn black and gooey. This buildup of goo can cause the fan to start wobbling and create instability in the mounting equipment.

As the equipment vibrates, there is movement or rattling in the metal ducts that surround it, and this will cause the flow of air to become uneven. As the chunks of dirt buildup break apart and fall off, this may cause noisiness when the air passes through. To remedy this, get a dry rag and clean the blades. You may have to use a degreaser, depending on how thick the gunk is. After cleaning thoroughly, check the fan for noise.

Step 2 - Check for Squeaky Parts

Since the exhaust fans spin so rapidly, they need to be able to move freely and smoothly. The drive belt needs to be tightened very firmly, and the drive wheels must be securely aligned with it. If the noise you are hearing is a squeaky one, it could mean you need to oil the fan a bit. This is easy to do. Before you oil the fan though, make certain the belt groove and the drive wheel are clean but don’t have any grease or dirt on them. Then, just use some sewing machine oil as a lubricant for the shaft of the fan blade.

You should also check to see if you have a loose belt, and if so, cut it off and replace it with a new fan wheel and motor belt. Start with the small wheel and put the new belt around it. Then, pull the belt around the large wheel as far as you can, and turn the blade of the fan slowly until you get a tight stretch of the belt around both wheels.

Step 3 - Make Sure the Fan Duct Is Clean

Look in the areas behind and in front of the fan to see if there are any dirt particles or other possible materials blocking up the area. When there is an obstruction and the air tries to move past it, it can cause a noisy vibration or rattling sound. Even worse, however, is that a dirt buildup might also get sucked into the duct pipes, and then eventually, the dirt will blow right inside your home. To avoid this happening, be sure to clean out any obstructions in front of or behind the fan duct on a regular basis.