Yes, that answer is a bit flip. But if a sound from a furnace is significant enough for you to ask the question, chances are high it’s an abnormal sound. You’re accustomed to the noise your home’s furnace makes—at least if you’ve already had it working for one winter—and when a new sound interrupts it, you’re right to be concerned. It might be a small issue, or it could be a warning you need to have furnace repair in Andover, MA from professionals.
(And we do mean professionals. Never try to go “do-it-yourself” with a furnace fix, and don’t let amateurs take on the work either.)
Let’s Be More Specific: What Noise?
The guide below to various furnace noises isn’t intended as a diagnostic for troubleshooting. Leave diagnosing the source of the noise to a licensed technician. This list is to give you an idea what may be afflicting the furnace so you know when to call for assistance.
- Mechanical shrieking and grinding: Looks like you’ve got a motor going bad. Probably the blower fan motor, which does a large amount of work to force air through the furnace and into the ventilation system. If this motor wears down, the bearings will start to go, which generates the shrieking sound. Fast repairs can replace the bearings and save the motor. A motor on the verge of burning out will make grinding or other unpleasant mechanical noises.
- Rattling: This might be a simple case of a loose door on the furnace cabinet. This is one problem you might be able to remedy yourself. However, it could point toward various loose parts inside the cabinet or broken sections of the ductwork.
- Clicking: You may hear some clicking at startup when the burners come on, and this is normal. Excess clicking might mean the burners are struggling to light, and there are various possible reasons for this. If you hear the clicking after the blower fan turns off, it’s possible the heat exchanger has a crack in it. This is a serious problem that can lead to carbon monoxide leaks! Shut off the furnace and call for a repair technician right away.
- Clanging and banging: Harsh metal clanging sounds can come from bend fan blades in the blower that are hitting the casing. The noise may be a more subtle scraping sound, indicating the wheel of the fan is loose and parts are rubbing together. For an older furnace, the sound may mean the fan belt has come loose and is striking parts of the casing. (Newer furnaces use direct motors for the blower fan.)
- Booming: The furnace comes on, and then a short time later you hear a booming (or “thwaaap!” noise) from the cabinet. The likely cause of this delayed burner ignition: too much unburned combustion gas has collected, and when the burners light, it all burns suddenly and creates this sound. The burner may need to be cleaned or repaired.