When a furnace makes unusual noises that aren't easily resolved, it's time to schedule an appointment with a heating and cooling service. The problem could be relatively minor, but even small issues will worsen. They also can shorten the lifespan of the furnace. Sometimes, a serious problem has developed and should be fixed promptly by a furnace repair technician.

Rattling

Rattling sounds can develop when bolts or screws come loose on the panels. The first step homeowners should take is tightening those devices. Ducts also can loosen over the years. Someone in the household probably can tighten the duct fasteners as well.

If these steps don't end the rattling sound, a repair service should be called. Another component inside the appliance might have come loose. The fan belt might be cracked or frayed — in which case, it must be replaced. 

Popping

It's normal to sometimes hear minor popping sounds when the furnace begins a heating cycle. Warm air moving through ducts that have cooled off causes the metal to expand and make that noise. A louder popping sound, though, may be connected with dirty burners.

Thuds and Banging

Thuds and banging before the furnace turns on may indicate that ignition is delayed. The noise essentially is from a small explosion. The gas has flowed in for too long before ignition takes place.

It's crucial to call for repair service when these noises first become evident. Miniature explosions can damage the furnace and crack the heat exchanger. A damaged heat exchanger sends exhaust fumes containing carbon monoxide into the home as the fans blow the air through the ducts. A cracked heat exchanger cannot be fixed. Replacing it is a very expensive project.

In addition, a safety mechanism is in place to shut the appliance down if the ignition delay is too long. That prevents a bigger and more serious explosion. Now the homeowners will need same-day or even emergency off-hours service to get the furnace running again.

Grinding

Grinding noises indicate a problem with bearings. The bearings may be worn-out, or they might simply need lubricating. If the homeowners haven't scheduled a furnace maintenance appointment in a few years, lack of lubrication could be the issue.

Concluding Thoughts

Scheduling an appointment with a company providing furnace service should be done quickly when the appliance makes unusual sounds that do not end after tightening bolts and other fasteners. If maintenance has not been completed within the past year, the technician can do that work along with repair service.