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Your Furnace Blower Motor: What It Is, How It Can Break Down, and How to Repair It

The job of a central heating system is to intake fresh air, warm it, then circulate it throughout the home via an air duct system until a desired temperature is achieved.

Just like any other mechanical device with moving parts, the furnace blower motor is susceptible to breakdowns. Read on to determine if your blower motor is malfunctioning and when to call a professional HVAC contractor to examine, repair or replace it.

What is a Furnace Blower?

Furnace blower assembly from Dor-Mar HeatingOne of the hardest-working parts of your home’s furnace is the blower motor. In a gas forced air furnace, it’s located in a box at the base of the furnace next to the air filter, where it draws return air through the filter. When switched on when requested by the thermostat and control board, the blower and motor push air across the burners in the combustion chamber where it gets heated, then the heat is transferred in the heat exchanger and blown out into the home’s ductwork.

The blower also functions during the air conditioning season by blowing return air across the evaporator coil to be cooled and pushed out into the home through the ductwork.

When the blower malfunctions, the central heating and air conditioning system cannot performs its job.

Just like any other mechanical device with moving parts, the furnace blower motor is susceptible to failure. Read on to determine if your blower motor is malfunctioning and when to call a professional HVAC contractor to examine, repair or replace it.

Indications of a Faulty Furnace Blower

The blower in a furnace is made up of a motor, fan blades in a cage (squirrel cage), and an electrical system to power it and control it. Any one or more of these parts can fail and prevent the HVAC system from doing its job.

One of the more common problems in a blower motor is the bearings. Bearings surround the motor shaft, allowing it to run smoothly at high RPM with almost no friction. When the bearings go bad, the motor may make a grinding or screeching sound, or not run at all because of the friction preventing the motor from turning.

The blower motor contains a capacitor, a device that stores energy to help the motor turn over with a jolt of extra electricity when it first starts up. If the capacitor goes bad, electricity may not reach the motor or it may not have enough electric to power the motor for its initial spin.

If the motor is packed with dust or dirt, or hasn’t been lubricated in a while (or ever!), the motor may overheat and cause an electrical short of mechanical failure, emitting an “unusual” odor or burning smell.

Modern blower motors contain electronics to prevent them from overheating, instead they shut down to prevent self-inflicted damage. Once the problem is resolve that’s causing the motor to overheat (such as friction, dust or dirt, or bad bearings) the motor will run normally. An indicator of this problem might be the furnace running for a short while, then shutting down, then running again after it cools down.

Airflow Issues

Weak or non-existent airflow from the vents usually means that something is impeding it from doing its job. Sometimes, furnace filters can get so badly clogged they prevent the blower from getting enough air. We’ve seen filters that are so clogged, and the blower worked so hard to suck air, the filter is pulled into the birdcage (or nearly pulled into it). The filter is a great place to start when determining furnace issues.

Faulty Belt vs Faulty Blower

Many modern furnaces are direct drive, meaning the squirrel cage/fan is connected directly to the shaft coming off the blower motor. Other furnaces may use a belt-driven system, where the motor shaft connects to a pulley and drive belt, connected to turn the fan. Sometimes the belt can stretch or the tension can slip, preventing from turning the fan at the proper speed. Like a v-belt on your automobile, the belt should be inspected and adjusted regularly and replaced occasionally to ensure the system works properly.

Can a Faulty Blower Be Repaired?

When a blower doesn’t turn on, our experienced HVAC technicians check to ensure the electrical system is providing power to the motor, and the capacitor is functioning optimally. Frequently, the capacitor may have to be replaced (they are sealed and not serviceable). Frequently, our technicians will remove the blower assembly from the furnace for a detailed inspection. First, he’ll ensure the fan blades, squirrel cage and motor are vacuumed to remove excess dust and dirt. He may lubricate the motor (if appropriate, as some motors are sealed and not serviceable) as well, and test all electrical connections. An excess buildup of dust can cause serious damage to the blower that could be prevented with routing maintenance. If the motor fails any tests, he may recommend a replacement if the motor cannot be serviced.

Can Furnace Blower Problems Be Prevented?

The single best thing you can do to prevent furnace blower problems is to have your furnace serviced by a professional HVAC technician annually. He will clean it to remove excess dust buildup, lubricate any moving parts that require it, and replace drive belt if required. It’s always best to have your furnace checked out before you need it – rather than calling us out on the coldest night of the year because your furnace isn’t running.

Of course, the furnace blower is just one part of a complex system that keeps your home at a comfortable temperature year-round. Other parts of the system can wear out, get dirty, or break. So the best way to prevent any of these issues is to have your HVAC equipment serviced annually.

Dor-Mar to the Rescue!

Schedule an appointment for HVAC system installation, troubleshooting or maintenance with us today by using our online contact form, or call one of our seven neighborhood offices listed below. We pride ourselves on our customer-focused service, and our reviews show it.

NEWARK  740.345.6639 • COLUMBUS 614.238.6689 • DUBLIN 614.545.8939 • REYNOLDSBURG 614.365.1579 • WESTERVILLE 614.381.1540 • GROVE CITY 614.595.3098 • ZANESVILLE 740.454.2420

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