> By: The Cooling Company
Key Takeaways
- Start with the filter, blower, and loose panels to stop many noises quickly.
- Tighten screws, secure duct hangers, and replace clogged filters before doing more work.
- Shut the furnace off and call a technician for gas smells or loud combustion bangs.
N/A: Quick reminder
This short section keeps one required term visible and offers a clear reminder about safety and scope. If a section of your furnace involves gas, flame, or live wiring, stop and call a licensed technician. Do not assume all repairs are safe for a homeowner.
The items below focus on low-risk, quick fixes you can safely try with the power off. These fixes include filter changes, tightening panels, and securing loose duct hangers. They often stop rattles, whistles, and light hums in 15 to 45 minutes. If you smell gas, hear loud combustion bangs, or a CO alarm sounds, evacuate and call emergency services.
What sound is the furnace making?
Make a short note of the sound type and when it happens. Describe the noise as squeal, hum, rattle, bang, or whistle. Pay attention to whether it occurs at startup, during steady run, or at shutdown. That timing helps narrow the likely source to the blower, ignition, or ducts.
A short phone recording is helpful to show a technician. Many pros match sound patterns to parts and bring the right tools and parts on the first visit. Keeping notes saves time and may cut diagnostic cost.
Is the noise coming from the blower?
Switch fan modes at the thermostat to see whether the sound changes with fan speed. If the noise stops when the fan is off, the blower or motor is a likely source. Dirt build-up on the blower wheel, an unbalanced wheel, or worn bearings cause scraping and humming sounds.
Always cut power at the service switch and breaker before opening panels. Inspect the blower wheel for dust buildup, wobble, or loose set screws. If you see damaged parts or are not comfortable, stop work and call a technician.
What is making my furnace noisy?
Listen closely while the furnace starts, runs, and shuts down. Timing and tone narrow down likely sources. Startup bangs point to ignition or combustion issues. Continuous hum often signals the blower motor. Intermittent rattles may be loose panels or duct hangers.
Stand near the unit and the main return to locate where noise is loudest. Tap duct sections lightly while the system runs to check for vibrating sections. A quick visual and listening check often rules out most common causes before you remove parts.
Are vibrations from the ductwork?
Metal ducts can rub joists or float on loose straps and make buzzes and rattles when air pulses pass. Small gaps at seams and flex connectors also add low-frequency vibration that travels through framing. These sounds often change with fan speed.
Feel for vibration at hangers and sealed joints while the blower runs. Seal small gaps with duct mastic or foil HVAC tape. Add rubber isolators where metal meets framing to break vibration paths. If ducts are undersized or badly damaged, call an HVAC pro for a permanent fix.
What indicates delayed ignition?
A loud bang at startup often means delayed ignition. Gas accumulates in the combustion chamber and then ignites in a pulse. This pulse stresses the heat exchanger and venting and may cause cracking over time.
Technicians inspect burner ports, ignition timing, and gas pressure to correct delayed ignition. Cleaning or adjusting burners typically fixes the problem. Repeated events need a prompt professional evaluation to avoid long-term damage.
Could a cracked heat exchanger be noisy?
A crack in the heat exchanger does not always make an audible sound. It can change how the cabinet vibrates and create new noises. The main risk is leakage of combustion gases, including carbon monoxide, into the home.
Any suspicion of a cracked exchanger is an emergency and requires immediate inspection by a licensed technician. Do not attempt to repair a heat exchanger yourself. Licensed pros perform pressure and combustion tests and visual inspection.
What quick DIY fixes should I try first?
Start with low-risk tasks that often stop common noises in 15 to 45 minutes. Change the air filter, tighten access screws, and inspect visible duct hangers. These steps use common tools like a screwdriver and a new filter.
Move on to cleaning the blower wheel and checking belts only if you are comfortable and have cut power. Do not work on gas or live electrical parts. If you find damaged wiring, a gas smell, or persistent combustion noises, shut the system down and call a licensed technician.
How to clean a blower wheel safely
First, cut power at the furnace switch and the breaker. Remove the access panel and unhook the blower assembly per the furnace manual. Use a soft brush and vacuum to remove dust from the wheel, then inspect for balance and set-screw tightness.
If the wheel shows damage or heavy corrosion, stop and call a pro. Reinstall the wheel carefully, check clearances, and test with the panels off at low speed before closing the cabinet.
How to check and tighten duct hangers
Locate noisy runs by listening while the blower runs. Tap the duct and listen for resonant sections. Tighten loose hangers and straps with sheet-metal screws or add rubber insulators between metal and framing to reduce vibration.
If a duct must be re-supported, use a sturdy hanger and avoid pinching the duct. For flexible ducts, ensure the flex is not overly stretched and that the connector is well sealed.
When to replace belts and pulleys
If your furnace uses a belt drive, a squeal often signals a loose or worn belt, or a misaligned pulley. Turn the power off and inspect the belt for cracking or glazing. Check pulley alignment and tension per the manufacturer specs.
Replace belts only with the correct size and type. If pulleys are scored or bearings are noisy, replacement of the pulley or motor may be necessary. If you lack the tools or experience, hire a technician to ensure proper tension and alignment.
When is a noisy furnace an emergency?
Know the warning signs that require immediate action. Loud bangs at startup, a strong gas smell, or a carbon monoxide alarm are emergencies. If you see or smell these signs, leave the home and call emergency services or your gas company from a safe location.
Never restart a unit after an emergency noise without a licensed inspection. Delaying checks risks heat-exchanger damage, CO exposure, or a gas leak. A quick shutdown and call protect your family and allow safe diagnostic testing.
Does loud banging mean delayed ignition?
Yes. Loud bangs at startup often indicate delayed ignition where gas accumulates before a forceful burn. The result is a pressure pulse that stresses the heat exchanger and venting. Repeated events can cause cracks.
A technician will inspect the burner ports and ignition timing and check gas pressure. Cleaning and adjustment usually solve the issue. Persistent problems may lead to replacement of ignition components.
Are combustion noises a carbon monoxide risk?
Abnormal combustion sounds can point to incomplete combustion and elevated carbon monoxide (CO) risk. Dirty burners, wrong gas pressure, or blocked venting are common causes that affect combustion quality.
Every home should have at least one working CO detector near sleeping areas. If a CO alarm triggers, leave immediately and call emergency services. After responders clear the house, have a licensed HVAC contractor test combustion and measure CO levels.
What to do if you smell gas
If you smell a strong gas odor, leave the building immediately. Do not switch lights or use phones inside. From a safe distance, call your gas company or emergency services. Do not return until the utility or emergency responders allow it.
Once cleared, have an HVAC pro inspect gas piping, fittings, and the furnace for leaks. Keep records of the service and any repairs performed.
How much will common repairs cost?
Costs vary by part, labor, and access difficulty. Simple items like filters, clips, and screws usually cost under $100. Blower motors, capacitors, and control boards often fall in the mid-hundreds when parts and labor are combined. Heat exchanger repair or replacement is usually the most expensive repair and can reach into the thousands.
Always ask for written estimates that separate parts and labor. Get at least two quotes for major repairs to compare value and warranty coverage. Consider unit age and expected life when deciding between repair and replacement.
What are typical costs for a new blower motor?
Blower motor replacement often ranges from about $300 to $900. Basic permanent-split-capacitor (PSC) motors are near the low end. ECM and high-efficiency motors cost more and may require control work.
Labor and access complexity affect total price. If the motor sits deep in an air handler or requires custom mounting, expect higher labor charges. Ask for a parts list and labor hours on the estimate.
How much to replace a heat exchanger?
Heat exchanger replacements commonly range from roughly $1,200 to $3,500 or more. Older or uncommon models can be pricier. Many contractors recommend full furnace replacement for very old units when exchanger costs approach unit value.
Replacement requires venting and combustion testing afterward. Get multiple written estimates and confirm that the contractor will perform required safety tests and provide warranty details.
How to evaluate estimates and warranties
Compare estimates that list parts, labor hours, and warranty terms. Beware of vague quotes that do not state part brands or labor rates. Ask whether parts carry factory warranties and how long labor is guaranteed.
For major work, request before-and-after photos of failing components and a clear scope of work. A reputable contractor will provide documentation and explain options plainly.
Need HVAC service help in Las Vegas?
If you live in Las Vegas, Henderson, or North Las Vegas and need a fast, local response, call The Cooling Company at 17029308411. Their NATE-certified technicians can diagnose noisy furnaces, run CO and gas tests, and repair or replace parts to code. They offer written estimates and photos of failing components to help you decide.
If you are outside their area, ask any contractor for NATE-certified technicians and proof of state licensing for gas work. Always check reviews and ask for written diagnostics before approving major repairs.
What happens during a diagnostic visit?
A technician measures airflow, motor current, and combustion gases. They inspect belts, bearings, electrical components, and ducts for loose hangers or leaks. Testing includes CO and gas safety checks and a written report with photos of failing parts.
Minor repairs are often completed the same day with homeowner approval. For major work, the tech provides options, timelines, and cost estimates backed by photos and test results.
How to prepare for a service appointment?
Clear access to the furnace and the thermostat so the technician can work without delay. Gather maintenance records, receipts, and warranty documents to help the technician assess past service and parts used.
Note when noises occur and whether they start at warm-up or during steady run. Secure pets and plan to be available to review findings and approve repairs. If you are outside the Las Vegas area, ask for NATE certification and written diagnostics before work begins.
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Sources and notes
Critical safety note: Do not attempt gas, combustion, or live-electrical repairs unless you are licensed and trained. For any smell of gas, loud combustion bangs, or activated CO alarms, evacuate and call emergency services.
About The Cooling Company
The Cooling Company has been serving the Las Vegas valley with professional HVAC services for over a decade. Our team of licensed, NATE-certified technicians specializes in air conditioning repair, heating system maintenance, and complete HVAC installations. We're committed to providing honest, reliable service with upfront pricing and a 100% satisfaction guarantee on all work performed.
- Phone: (702) 930-8411
- Reviews: 4.9/5 stars (500 reviews) - See reviews
Service Areas
We proudly serve homeowners and businesses throughout the Las Vegas metropolitan area, including Las Vegas, Henderson, and North Las Vegas. Our service technicians are available for same-day appointments in most areas, with emergency service available 24/7 for urgent HVAC issues.