3 Reasons Your Furnace Inducer Blower Is Making Noise

Posted on: 2 March 2023

Did you know that your furnace uses two separate blowers? The main house blower pushes air warm through your ductwork and into your home, while the inducer motor serves a very different purpose. This secondary blower creates negative pressure that pulls combustion gases away from the burners and through the exhaust flue. Like your main blower, the inducer motor can eventually fail.

A noisy inducer blower is usually relatively easy to spot. This blower will turn on before your furnace ignites, so it will often be one of the first things you hear during the ignition sequence. If you notice some strange sounds before your furnace ignites, it may be due to one of these three common inducer blower issues.

1. Foreign Debris

Most inducer blowers use a centrifugal design with the impeller (the fan wheel) inside a metal or plastic housing. A separate motor turns the wheel, pulling air through the inducer and away from the furnace blowers. The internal impeller is similar to the paddle wheels found on old steamships, so it's easy to see how foreign objects or debris can become trapped on the wheels and turn with them.

If you can hear a rattling or bouncing noise as the impeller comes on, there's a good chance there's something stuck inside. Since the exhaust flue exits outside, animals or insects can sometimes enter the blower housing. A broken impeller blade can also become trapped and rattle around. These objects can cause damage to the inducer, so it's crucial to have a technician investigate the noise right away.

2. Pitch Problems

Modern, high-efficiency furnaces extract so much heat from the exhaust stream that water condenses and drips back through the exhaust flue and into the condensate tube. Under normal circumstances, this water drips away harmlessly and drains into your home's plumbing or another outlet. However, pitch problems (either the vent pipe or parts of the furnace itself) can cause water accumulation.

Sometimes, water can accumulate inside the inducer motor housing. Since the impeller occupies most of the internal space in the housing, a small amount of water will inevitably cause a noticeable sloshing noise. This water can damage the impeller or cause it to rust and fail. Additionally, vent pitch issues can be potentially hazardous. Either way, water in the inducer is a sure sign that you need an expert.

3. Motor Failures

Of course, the motor is the most obvious failure point for any blower. Electric motors will wear out over time, with the bearings typically being the most common failure point. Premature bearing failure is more common on unsealed bearings when maintenance is neglected — but can occur on any blower motor.

Bearing failures typically produce loud, grinding noises that may be audible from a distance or even through your home's ductwork. As the inducer motor spins up, you may also hear a squealing or rattling noise. It's critical to address bearing failures sooner rather than later since the motor will eventually fail and stop your furnace from functioning.

To have your unit inspected, contact a heating contractor in your area.