It’s normal for a furnace to make some noise: a low hum, a soft whoosh of air, or a click or two at startup. What’s not normal is a sound you’ve never heard before, one that’s unusually loud, or one that recurs every cycle.
If that’s what brought you here, take a breath. Most furnace noises point to a specific issue, and most of them are fixable. Here’s how to decipher what your furnace is telling you, and when it’s time to call a professional.
Banging or Booming
A loud bang at startup usually means delayed ignition; gas builds up before catching all at once. Dirty burners, a weak igniter, or a dirty flame sensor are the usual causes.
Repeated banging can crack your heat exchanger over time, which means an expensive repair and a carbon monoxide risk, so if it happens more than once, call us rather than wait it out. A softer boom right after startup or shutdown is just ductwork adjusting to the heat, and that’s normal.
Whistling
Whistling almost always signals air being forced through an improper opening. The usual reasons include a dirty, clogged air filter; closed or blocked supply vents; a blocked return; or leaky and undersized ductwork.
Start by checking your filter; it’s the most common cause and the easiest to inspect yourself. Then, walk through your home and ensure every register is open. If the whistle persists, it’s worth having us take a look, as restricted airflow forces your furnace to work harder than necessary, which will impact your energy bill before manifesting in other ways.
Clicking
A single click when your furnace starts up and shuts down is normal, indicating your igniter and relay are functioning. Repeated clicking with no ignition, however, is different. This means your furnace is attempting to light the burners but isn’t catching, and it keeps trying. This is usually due to a dirty or failing flame sensor, a worn-out igniter, or a gas valve that isn’t opening correctly.
Left unaddressed, this is precisely how a homeowner ends up without heat on the coldest night of the year. If your furnace is clicking and not lighting, that’s an issue to call in rather than postpone.
If You Smell Gas
This is not a “wait and see” situation. If you ever smell gas near your furnace, open your windows and doors, get everyone out of the house, and call your gas company or 911 from outside before calling anyone else, including us.
For every other noise on this list, there’s no need to panic. It’s simply a reason to call someone you trust and let them handle it.
We’ve been keeping Northern NJ homes warm since 1985, and a strange noise from your furnace is exactly the kind of issue we’re equipped to resolve, day or night. We’re on call 24/7.
Hearing something you can’t explain? Contact us, and we’ll get it sorted.
