Furnace Making Noise in Las Vegas: What the Sound Is Telling You

Short answer: A furnace makes some noise on every cycle: a click, the draft fan, the burner lighting, then the blower. What matters is when the new noise happens and what it sounds like. Note whether it's at start-up, while running, with no heat, with no air, or when the system is off. Then use the sections below. Check the filter and the vents first. For anything louder or new, turn the heat off at the thermostat and schedule a visit rather than running it to see if it goes away.

If you ever smell gas (rotten eggs or sulfur), leave the house and call 911 or Southwest Gas from outside.

Colton Air Conditioning schedules heating visits Monday–Friday, 8am–5pm.

Why Las Vegas furnaces get noticed in the fall

Valley homes run the AC most of the year and the furnace only a few months. The burner side sits unused through summer, so the first cool nights are when people hear the start-up sequence again and notice anything that changed. Plenty of those sounds are normal. Some are worth a look before the coldest weeks of winter.

Normal furnace sounds

A typical gas furnace cycle goes roughly like this:

1. A click at the thermostat or control board as heat is called.
2. The draft inducer fan starts (a steady whir).
3. A click or tick as the ignitor works, then a soft whoosh as the burners light.
4. After a short delay, the main blower starts and warm air comes out the vents.
5. When heat is satisfied, the burners go out and the blower runs a little longer, then stops.

Light ticking as metal ducts warm up and cool down is also common. If what you hear fits this pattern and the house is warming, it's likely fine.

Common noise types and what they usually mean

These are general patterns, not a diagnosis.

• Rattling. Often something loose: a panel door not seated, a loose screw, a duct joint, or debris in the blower or inducer area. Check that the furnace door is fully closed.
• Banging or booming when the burners light. Can point to the burners lighting late, dirty burners, or ductwork flexing as it heats ("oil-canning"). A loud boom on ignition is one to have looked at. Turn the heat off at the thermostat and schedule a visit.
• Squealing or screeching. Often a blower motor or inducer motor bearing, or a belt on older belt-drive blowers.
• Humming or buzzing. Can be a motor working hard, a capacitor, or a transformer or relay. A steady low hum can be normal. A loud buzz with no blower running is not.
• Clicking. Normal at start-up. Repeated clicking with no flame can mean the ignition isn't completing. That can be an ignitor issue, a flame sensor issue, or a safety switch stopping the sequence.
• Scraping or grinding. Usually something rubbing in the blower. Turn it off at the thermostat and schedule a visit.

Furnace making noise when starting up

Start-up is where most new noises show up, because that's when parts move from cold to hot. A click and a whoosh are normal. A boom, repeated clicking without lighting, or a rattle that starts with the inducer fan are worth noting. If the burners light and then go out after a few seconds, a dirty flame sensor is a common cause. See furnace flame sensor. For ignitor clicks with no flame, see the ignitor section in furnace pilot light.

Furnace making noise when running

Once it's running, most noise comes from the blower and the airflow. Rattles and squeals usually trace back to the blower motor, its mounting, or a loose panel. A whistle often means airflow is restricted. Check the filter, and make sure supply vents and return grilles aren't blocked. Restricted airflow can also make the furnace overheat and shut off early. See furnace limit switch.

Furnace making noise but no heat

If you hear the furnace trying (clicking, the inducer running, or the blower running) but no warm air, the start-up sequence is stopping partway. Common reasons include the burners not lighting, the flame not being detected, or a safety switch opening. Start with the thermostat set to Heat and the furnace switch on. Then follow heater not working. If air is moving but it's cool, see heater blowing cold air.

Furnace making noise but not blowing air

If you hear humming or the burners running but nothing comes out of the vents, the blower may not be starting. That can be a blower motor, its capacitor, or a control issue. A furnace whose blower doesn't start will usually shut its burners off on a safety limit. Turn the heat off at the thermostat and schedule a visit rather than cycling it repeatedly.

Furnace making noise when off

Some sounds happen with the furnace off. Ticking ducts cooling down after a cycle are common. A click with no cycle following can be the thermostat or control board. A hum when nothing is running can be a transformer or a relay that's stuck. Running water or gurgling near the furnace can be the condensate drain on high-efficiency models. See furnace leaking water. If the furnace starts and stops often on its own, see furnace short cycling.

What to check yourself (once)

1. Filter. Replace it if it's gray or packed, with the size printed on the frame.
2. Vents and returns. Open, and not blocked by furniture or rugs.
3. Furnace door. Fully seated. Many furnaces won't run with the door off, and a loose door rattles.
4. Thermostat. Set to Heat with the setpoint a few degrees above room temperature. Fan on Auto.

Don't open the burner compartment, oil motors, or take apart the blower yourself.

When to schedule a visit

Schedule a visit when the noise is new and loud (booming, grinding, screeching), keeps coming back after the checks above, or comes with no heat or no air. A pre-winter furnace tune-up is also a good time to have a minor noise checked.

When you call, tell us when it happens (start-up, running, off), what it sounds like, and whether the house is still heating. A short phone recording of the sound helps.

Colton Air Conditioning · 6545 S. Fort Apache Rd Ste 135 #467, Las Vegas, NV 89148 · Nevada license 0092120 · Monday–Friday, 8am–5pm · (702) 738-6976 · Book Online

Saturday and Sunday are closed.

Yearly maintenance: See our Comfort Club maintenance plans.

FAQ

Why is my furnace making noise when starting up? A click, a fan whir and a soft whoosh are normal. A loud boom, repeated clicking without the burners lighting, or a new rattle are worth having checked.

Why is my furnace making noise when running? Usually the blower or airflow. Rattles and squeals often come from the blower motor or a loose panel. Whistling often means a dirty filter or blocked vents.

Why is my furnace making noise but there's no heat? The start-up sequence is likely stopping before the burners stay lit. Check that the thermostat is on Heat and the furnace switch is on, then schedule a visit if it continues.

Why is my furnace making noise but not blowing air? The blower may not be starting. Turn the heat off at the thermostat and schedule a visit rather than cycling it repeatedly.

Why does my furnace make noise when it's off? Ducts ticking as they cool is common. A hum or click with nothing running can be a transformer, relay or thermostat.

Is a banging noise from my furnace dangerous? A loud boom when the burners light should be looked at. Turn the heat off at the thermostat and schedule a visit. If you smell gas, leave the house and call 911 or Southwest Gas from outside.

What hours can I reach Colton? Monday through Friday, 8am to 5pm.

Call (702) 738-6976 or Book Online. License 0092120. Hours Monday through Friday, 8am to 5pm. Saturday and Sunday are closed.