Introduction: Common Furnace Issues and How to Fix Them
When it comes to large gas furnaces — like 80,000 BTU gas furnaces used to heat larger homes — you rely on them to keep your home warm and comfortable through the coldest months. But like any piece of machinery, furnaces can encounter problems from time to time. Whether it's something simple like a dirty filter or a more complex issue like a malfunctioning gas valve, a little troubleshooting can go a long way in keeping your furnace running efficiently.
In this blog, we’ll help you tackle some of the most common furnace problems and offer tips for troubleshooting each issue. From pilot light issues to uneven heating, strange noises, and efficiency drop-offs, we’ll guide you on how to fix things yourself when possible — or know when to call a pro.
Let’s dive into the most common problems and how you can troubleshoot them effectively.
1. Pilot Light Issues: Why Won’t It Stay On?
The pilot light is essential for your furnace to operate, and when it won’t stay lit, you’ve got a problem. The pilot light is the small flame that ignites the gas coming into your furnace. If it’s out or flickering, your furnace won’t be able to create heat. Here’s what might be going on and how you can troubleshoot it.
Possible Causes of Pilot Light Issues
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Dirty Pilot Light or Thermocouple
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The thermocouple is a safety device that senses if the pilot light is burning. If it gets dirty, it can’t detect the flame properly, causing the gas supply to turn off.
How to fix it:
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Turn off the furnace and let it cool down.
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Clean the thermocouple with a fine brush or cloth. If the thermocouple appears damaged, it might need to be replaced.
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Clean the pilot light using compressed air or a small wire brush to remove any dust or debris.
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Clogged Pilot Tube
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Over time, the pilot tube can become clogged with dirt or debris, causing a weak or inconsistent flame.
How to fix it:
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Turn off the furnace and ensure the gas supply is turned off.
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Clean the pilot tube using compressed air or a soft brush to remove the blockage.
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Faulty Gas Supply
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If your gas supply isn’t working properly, the pilot light won’t stay lit. This could be due to a gas valve issue or a gas line leak.
How to fix it:
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Check the gas valve: Make sure it’s in the “on” position. If it’s not, turn it on and try relighting the pilot light.
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Listen for a gas leak: If you suspect a gas leak, turn off the gas immediately and contact a professional technician.
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Malfunctioning Thermostat
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Sometimes, a malfunctioning thermostat can cause the furnace to shut down, which can affect the pilot light.
How to fix it:
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Check the thermostat settings and ensure the temperature is set above the current room temperature.
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Replace the thermostat batteries if applicable.
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2. Uneven Heating: Some Rooms Are Warm, Others Are Cold
If you notice that certain rooms in your home aren’t heating as well as others, it could be a sign of an airflow or furnace issue. Uneven heating can make your home uncomfortable and lead to higher energy bills if left unchecked.
Possible Causes of Uneven Heating
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Clogged or Dirty Air Filters
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A dirty air filter is the most common cause of poor airflow. When filters are clogged, air can’t flow freely, causing certain rooms to receive less heat than others.
How to fix it:
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Replace the air filter every 1-3 months, depending on usage. This will improve airflow and prevent dust buildup inside the furnace.
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Blocked or Closed Vents
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Sometimes, vents can be accidentally closed or blocked by furniture or other objects. This can restrict the airflow and cause uneven heating in specific areas.
How to fix it:
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Ensure vents are open and unobstructed by furniture, rugs, or curtains.
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Inspect ductwork to make sure no ducts are collapsed or leaking air (US EPA).
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Ductwork Leaks
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Leaky ducts can cause heated air to escape before it reaches the rooms, leading to uneven heating and higher energy costs.
How to fix it:
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Seal duct leaks with special duct tape or consider having a professional duct sealing service.
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Improper Furnace Size
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If your furnace is too small or too large for your home, it may not be able to heat the entire space evenly. An undersized furnace will struggle to heat the home, while an oversized unit will cycle too quickly, not providing consistent warmth.
How to fix it:
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Have a professional perform a load calculation to determine if your furnace is appropriately sized for your home. If not, upgrading to a correctly sized furnace, such as an 80,000 BTU gas furnace, could resolve the issue.
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3. Strange Noises: Is My Furnace in Trouble?
If your furnace starts making unfamiliar or loud noises, it’s essential to investigate. Most of the time, strange noises are harmless, but they can also signal that something is wrong with your system. Here are some of the most common furnace noises and what they might mean.
Common Furnace Noises and Their Causes
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Banging or Popping Noises
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Banging or popping sounds often happen when the furnace’s ductwork expands or contracts due to temperature changes. This is generally normal, but loud or frequent popping could indicate a pressure problem or a clogged filter.
How to fix it:
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Replace the air filter and check for proper airflow. If the noise continues, it could be due to dirty burners or an issue with the gas flow.
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Whistling or High-Pitched Sounds
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A whistling sound could be caused by air leaks in the ducts, restricted airflow, or an obstruction in the furnace.
How to fix it:
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Inspect the ducts for gaps or leaks, and seal any openings. Clean the filters to ensure proper airflow.
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Rattling or Vibrating Sounds
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Rattling or vibrating sounds can come from loose panels or components within the furnace.
How to fix it:
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Tighten loose parts or panels. Ensure that all screws and bolts are secure. If the noise persists, it may indicate an internal mechanical issue that requires professional attention.
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Squealing or Screeching Sounds
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If you hear a squealing or screeching noise, it may be a sign that the blower motor or fan belt is worn or needs lubrication.
How to fix it:
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Lubricate the blower motor and check the fan belt for wear. If the motor or belt is damaged, it may need to be replaced (ResearchGate).
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4. Efficiency Drop-Offs: Furnace Not Running as Efficiently as It Should
Is your furnace running inefficiently? Efficiency drop-offs can lead to higher heating costs and more frequent breakdowns. Several factors can cause a furnace to lose its efficiency.
Possible Causes of Efficiency Drop-Offs
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Dirty or Clogged Air Filters
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As mentioned before, a clogged filter can reduce airflow and cause the furnace to work harder. This leads to higher energy consumption and less efficient heating.
How to fix it:
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Replace or clean the air filter regularly to ensure proper airflow and optimal performance.
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Dirty Burners
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Over time, dust and dirt can accumulate on the furnace’s burners, reducing their ability to produce heat efficiently. Dirty burners can also cause incomplete combustion, leading to carbon buildup and system failure.
How to fix it:
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Clean the burners by removing any dust and dirt with a soft cloth or compressed air. If the burners appear damaged or excessively dirty, consult a professional.
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Malfunctioning Thermostat
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A malfunctioning thermostat can cause the furnace to run longer than necessary, leading to wasted energy. If your thermostat is incorrectly calibrated, your furnace might overheat your home or fail to heat it properly.
How to fix it:
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Calibrate or replace the thermostat. You can also consider upgrading to a programmable thermostat for better control over heating schedules.
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Leaky Ductwork
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Leaky or uninsulated ducts can lead to heat loss before the air reaches its destination. This not only affects comfort but also reduces efficiency.
How to fix it:
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Seal any leaks in the ductwork using special duct tape. Consider having a professional conduct a full duct inspection to ensure efficiency.
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Old Furnace
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If your furnace is outdated or nearing the end of its lifespan, it will naturally become less efficient.
How to fix it:
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Upgrade to a high-capacity unit, like an 80,000 BTU gas furnace with a higher AFUE rating, which will save you money in the long run. Newer furnaces have better heat exchangers, more efficient blowers, and reduced energy consumption.
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When to Call a Professional
While many common furnace issues can be addressed by homeowners, some problems require professional expertise. It’s important to know when to call in an expert.
Call a Pro If:
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You smell gas: If you smell gas near your furnace, turn it off immediately, evacuate the area, and contact a technician.
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Your furnace is not igniting: If the furnace refuses to turn on and your troubleshooting has not fixed it, there may be a bigger issue with the gas line or igniter.
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You hear strange, loud noises: If the noises persist even after you’ve checked and cleaned the system, it could indicate an internal mechanical failure.
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Your furnace is leaking water: A water leak, especially from a high-efficiency furnace, could indicate a condensate drain issue or other serious problem.
Key Takeaways
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Pilot light issues: Often caused by dirty thermocouples, clogged pilot tubes, or faulty gas supply (ResearchGate).
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Uneven heating: Ensure proper airflow, inspect ducts, and check furnace size for your home’s needs (US EPA).
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Strange noises: Address banging, rattling, or whistling sounds by inspecting ducts, cleaning parts, and tightening loose components.
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Efficiency drop-offs: Replace filters, clean burners, and ensure proper thermostat calibration to maximize efficiency.
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When to call a professional: Always consult a pro if you smell gas, experience ignition problems, hear loud noises, or notice a water leak.
Conclusion: Keep Your Furnace Running Smoothly
Furnace issues can disrupt comfort, but many problems are easy to troubleshoot and fix with the right knowledge. Whether you’re dealing with a pilot light problem, uneven heating, strange noises, or efficiency drop-offs, you can take simple steps to get your 80,000 BTU gas furnace back to work. And when the problems seem beyond your expertise, don’t hesitate to call a professional HVAC technician for help.
By staying proactive with maintenance and troubleshooting, you can keep your furnace running efficiently, extend its lifespan, and protect the cost of your furnace by avoiding costly repairs down the road.
