Common Furnace Problems & Their Symptoms
Faulty heaters are more than a nuisance. They can pose a fire hazard, and gas furnaces can leak carbon monoxide into your home.
Call a professional technician if you notice any of the following problems:
- A furnace that won’t heat to the set temperature.
- Unusual odors, especially burning smells.
- Leaking tubes.
- Shorts in electric heating coils.
- Vents that fail to expel carbon monoxide.
- Carbon monoxide sensors that fail to shut down a defective unit.
- Faulty furnace wiring.
Identifying Furnace Problems: A Checklist
1. Uneven Heating
If the temperatures in your home range from Sahara Desert heat to Arctic tundra cold, check for any blocked or dirty air filters, which can restrict airflow.
Uneven heating could also be due to to:
- A faulty blower motor or fan control.
- Damaged ductwork.
- An improperly sized furnace.
- A malfunctioning thermostat.
- A dirty or clogged heat exchanger.
Most of these issues call for professional diagnosis and repair.
2. Strange Noises
Furnaces are rarely whisper quiet, but loud or unusual sounds usually indicate a problem:
- Clanging, vibrating: Something could be loose in the furnace.
- Squealing or screeching: A belt may have slipped or been damaged.
- Rattling: You may have an issue with the blower assembly or motor.
- Humming: A component could be on the verge of failure.
- Chirping: These sounds are expected at the start or end of the heating cycle. But if the chirping continues, you could have a problem with the blower wheel or motor.
- Popping or booming: These noises are often due to dirt and dust build-up in the system. It’s a quick fix but left unchecked, dirt can damage your furnace.
- Clicking: Repeated clicking could indicate a faulty flame sensor or a problem with your ignition. Don’t delay; get it fixed right away.
- Rumbling: If this occurs after shutoff, it’s a telltale sign of unburned fuel in the heat exchanger, which can lead to significant issues down the road.
- Hissing: A hissing sound could indicate a gas leak. Immediately turn off your furnace, leave the house, and call for professional help.
- Whistling: This could signal a clogged filter or a duct issue. It’s not a sound to ignore; your system’s efficiency is likely taking a hit.
- Banging: A loud bang or boom when the furnace kicks on could mean a delayed gas ignition, which is potentially dangerous and should be addressed ASAP.
- Thumping or bumping: These sounds may indicate a problem with the blower wheel. Get it checked out before more parts are affected.
- Rapid clicking or ticking: This could be due to a crack or leak in the heat exchanger — a life-threatening situation that can lead to carbon monoxide in your home.
- Grinding: Grinding noises are usually serious and may indicate a problem with the furnace’s blower motor. Call a technician if you hear this sound.
For all these problems, your safest bet is to contact a professional furnace technician who can get to the bottom of things and ensure your home stays cozy and safe.
3. High Energy Bills
While it’s normal for energy bills to fluctuate during the winter, any spikes should raise red flags. Potential causes include:
- An old, inefficient furnace: Aging furnaces lose efficiency, especially if poorly maintained. They consume more energy and drive up utility bills.
- Faulty thermostat: A malfunctioning thermostat can make your furnace run longer than necessary, increasing energy consumption.
- Poor insulation: Inadequate insulation can let warm air escape. Your furnace will work overtime to keep up.
- Clogged air filters: Dirty air filters restrict airflow, forcing your furnace to work harder to circulate warm air.
- Leaky ductwork: Cracks or holes in your home’s ductwork can let heated air escape before it reaches the rooms in your home.
- Unbalanced airflow: If the airflow in your system is improperly balanced, your furnace might struggle to distribute heat evenly, leading to overcompensation and high energy consumption.
- Incorrectly sized equipment: A furnace that’s too large or too small for your home is inefficient. An oversized unit will cycle on and off too often, using more energy, while an undersized unit will run constantly to keep up with the demand.
- Lack of regular maintenance: Regular furnace maintenance is crucial for efficient operation. If skipped, your furnace can develop more severe issues than increased energy usage.
- Inefficient blower motor: Older furnaces have less efficient blower motors than newer models. When these motors struggle, your furnace burns more energy.
- Corroded burners: Corroded burners can restrict gas flow and cause inefficient combustion.
- Faulty gas valve: If the gas valve isn’t supplying enough gas to the burner, the furnace will run longer to reach the set temperature.
- Improper venting: Poorly installed or maintained venting can create pressure imbalance and inefficiency within the heating system.
- Windows and doors: Improperly sealed doors and windows are primary heat loss areas.
4. No Heat at All
- Faulty thermostat: A defective thermostat may not signal the furnace to start the heating cycle.
- Tripped circuit breaker: Ensure your circuit breaker isn’t tripped and the furnace switch is turned on.
- Snuffed pilot light: If you have a gas furnace, check if the pilot light is lit. If it’s out, follow your manufacturer’s instructions to relight it.
- Lack of fuel: If your furnace runs on propane or natural gas, check if the fuel supply line is open and there’s fuel available.
- Blocked exhaust: An obstructed exhaust vent can cause your furnace to shut down as a safety measure.
- Faulty ignition sensor: A defective ignition sensor can prevent the furnace from igniting the fuel.
- Dirty or clogged filters: Excessively dirty or clogged air filters can restrict airflow to the point where no heated air reaches your living spaces.
- Faulty limit switch: The limit switch controls the fan that circulates heat. If it isn’t working correctly, you may not feel heat even though the furnace is running.
- Broken blower motor: A malfunctioning blower motor won’t be able to distribute warm air throughout your home.
- Corroded or cracked heat exchanger: An older heat exchanger can develop cracks or corrode, preventing it from effectively heating the air.
- Faulty control board: The furnace’s control board oversees all its functions. If it’s experiencing problems, your furnace might not produce heat.
- Failed transformer, capacitor, or fuse: These electrical components are vital for the operation of your furnace. Failure of any of them could result in no heat.
- Faulty gas valve: A malfunctioning gas valve will prevent gas from reaching the burner.
Suppose your furnace fails to produce heat, and you’ve already checked the thermostat, fuses, exhaust, filters, and pilot light. In that case, it’s time to call a professional to diagnose and resolve the issue.
The remaining items on the above list aren’t things you can fix yourself, and trying to do so could be dangerous.
5. Unusual Odors
- Burning dust smell: Dust can accumulate on the heat exchanger and in the ductwork. When the furnace comes on, this dust burns off and emits a distinct smell. It typically disappears after a few hours.
- Rotten egg smell: This smell could indicate a gas leak. Natural gas is odorless, but suppliers add a chemical that smells like rotten eggs to make leaks detectable. Turn off your furnace, leave the house, and call your gas company immediately.
- Electrical or metallic smell: An electrical or metallic smell might indicate that your furnace’s motor or blower is overheating or there’s a problem with the electrical wiring.
- Chemical smell: A chemical odor could be a sign of a cracked heat exchanger, which can lead to carbon monoxide leaks. This requires immediate professional repair.
- Moldy or musty smell: A moldy or musty odor can be a sign of mold in your furnace or ductwork. This can happen with excess humidity in your home or a duct leak.
Simple Checks & Tricks to Improve Furnace Efficiency
Heating bills can add up fast during the winter months, especially if you live in a larger, multi-story home, a poorly insulated older home, or prefer a toasty ambient temperature.
Regular maintenance can keep your furnace in peak condition and extend appliance life. A few dollars spent here and there will save you a bundle in the long run.
Here are some yearly maintenance tasks that can keep your furnace running smoothly and efficiently:
- Changing the air filter: Think of your vacuum cleaner. How well does it run when the filter clogs with dirt, grime, and cat hair? Exactly. Your furnace is no different, and it takes far more energy to pull and push air through a clogged filter versus a clean filter. Change the filter every three months or more often during periods of heavy use.
- Cleaning the area around the furnace: Keeping the furnace area clean can prevent dirt and dust from entering the system. Make sure to keep the site clear of storage and clutter.
- Inspecting the venting system: Periodically check your venting system for any signs of wear, blockage, or damage.
- Checking the thermostat: Regularly test your thermostat to ensure it’s working as it should.
- Annual service check: Scheduling a yearly furnace inspection with a professional technician can help identify and fix potential issues before they become serious.
- Annual tune-up: An annual tune-up can optimize your furnace’s performance, prolong its lifespan, and even reduce your energy bills.
- Duct cleaning: Dust and allergens can build up in your ductwork. A professional duct cleaning every 3-5 years can improve air quality and furnace efficiency.
Adding a Humidifier
Moist air has a higher heat index than dry air. It feels warmer. A simple trick to stay comfortable is to humidify your home during the winter and dehumidify it during the summer.
Insulating Ductwork & Sealing Leaks
A leaky water pipe is a household disaster — everyone springs into action to fix it ASAP. But leaky air ducts often go unnoticed. The problem may persist for years. Air leaks don’t cause the same catastrophic damage as water leaks, but they contribute mightily to high energy bills and general discomfort as heated or cool air fails to reach some corners of the house.
Seal these leaks with professional-grade metal-backed tape.
Insulation helps your ducts retain the heat (or cool air) as it travels through your home. Ductwork insulation can reduce heat loss by up to 60%. Check that your exposed heating ducts in unheated areas like the attic and crawl spaces are adequately protected.
Upgrading Your Thermostat
A programmable thermostat lets you set specific temperatures for different times of the day. This means you can lower the temperature when no one is home or sleeping and raise it again before you wake up or come home. This approach can save you a significant $$ on your heating bill.
When to Call Chief Repair
As your furnace ages and wears out, you’ll inevitably encounter a problem requiring professional repair.
In metro Los Angeles, the service to call is West Coast Chief Repair. 888-832-3599.
West Coast Chief Repair is an authorized dealer of trusted brands of heating equipment.
- We sell, install, and maintain furnaces to keep them in top condition.
- We repair broken or inefficient furnaces and replace old or damaged appliances beyond repair.
- All estimates are FREE; there’s no obligation to buy services. However, we’re confident you’ll choose Chief for your heating and cooling needs.
- We also do air duct repair and installation.
- All Chief technicians are licensed, certified, insured, and experienced.
Call us today. 888-832-3599.
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