20 Common Furnace Problems and Their Quick Fixes

Furnaces present a dependable and efficient method to maintain you heat throughout winter months. Sadly, like another dwelling equipment, these heating systems could encounter occasional points that require troubleshooting and restore.

The issues can come up resulting from a scarcity of HVAC maintenance or defective elements. Different components, reminiscent of thermostat malfunctioning and leaky ducts, will also be accountable for any subject that develops within the furnace. 

Learn on for detailed info on widespread furnace issues that you would be able to face and attainable options.

1. Ignition Issues

If the furnace fails to ignite, it might be resulting from a defective spark igniter, blocked gasoline valve, or inadequate gasoline provide. Newer furnace fashions don’t have a standing pilot for ignition; moderately, they use electrical elements. In case of points with electrical ignition, your furnace may cycle on/off regularly, produce little to no warmth, otherwise you is likely to be coping with an overactive blower. 


  1. For older typical furnaces, flip off the furnace energy and examine the heating aspect. If the igniter is cracked or broken, it received’t have the ability to generate sufficient warmth to ignite the gas. Contact an HVAC technician and change it. 
  2. If the burner is soiled, it may well trigger issues with ignition. Clear it with a gentle brush or vacuum cleaner to take away any grime or particles.
  3. Make sure the gas reaches the furnace. Test the gas line and the gas filter, and ensure they don’t seem to be clogged.
  4. Confirm the ignition system. Ensure the ignition system is working accurately. Test the circuit board, wiring, and different elements.
  5. For newer fashions, attempt changing the filters and checking the ability and gasoline traces. 
  6. Name a technician for an in depth checkup if these easy options don’t work. 

2. Furnace Runs Non-Cease

In the event you discover your furnace is working repeatedly, there are two causes for that. Both your thermostat is ready to fan mode, or there’s one thing improper with the fan restrict management change. 


Test your thermostat, and if it’s set to fan mode, the answer is to modify it to ‘auto’ mode. This can be sure that the fan solely runs when your system is heating. 

The fan restrict management change displays the temperature contained in the furnace and alerts it to show off when the set temperature is reached. If it’s not working, the furnace will carry on working. For troubleshooting, examine the fan motor change. If it appears to be like okay, reset it to repair the difficulty. If it appears to be like broken, name a technician to switch it. 

3. Pilot Mild Issues

Pilot gentle points are one of many widespread causes your furnace isn’t working. The sunshine can fully flip off, or it’s possible you’ll discover steady flickering. The pilot gentle on gasoline furnaces can exit resulting from drafts, debris-filled gasoline tubes, or soiled pilot burners. A defective thermocouple, which is a sensor that measures temperature, may trigger the gasoline provide to close off. In the event you discover a yellow pilot gentle, it’s almost definitely resulting from extra carbon monoxide in your furnace. 


  1. Relight the pilot fireplace if it had gone out. In case your furnace is working tremendous, the difficulty is resolved. 
  2. If relighting doesn’t work, examine the furnace strain change. This change is designed to close off the gasoline when the pilot gentle goes out. If the change isn’t working, change it. 
  3. Test the thermocouple; if it’s defective, change it. 
  4. Make sure the gasoline valve is open, and the availability line isn’t clogged or blocked. 
  5. Lastly, examine the pilot gentle meeting. Make sure the pilot gentle is in good situation and the pilot gentle tube is obvious of particles.
  6. Within the case of a yellow pilot gentle, it’s greatest to contact your native furnace technician, as carbon monoxide is harmful to cope with. 

4. Thermostat Having Points

In case your furnace fails to make your own home surroundings comfy, think about checking the set temperature in your thermostat. Typically, the thermostat can stop working and never ship the right sign to the furnace. The unfastened wiring may trigger points. Another excuse your thermostat is inflicting issues is a scarcity of upkeep. Mud and grime can intrude with the thermostat’s capability to learn and reply to temperature adjustments. Incorrect thermostat location may compromise the effectivity of the furnace.


  1. Strive resetting your thermostat if it’s exhibiting incorrect readings. 
  2. In case your thermostat has hassle reaching your set temperature, examine its calibration. Right here’s learn how to calibrate your thermostat
  3. To examine the unfastened wiring, detach the thermostat from the wall and look at the wire connections. Ensure the wires popping out of the thermostat are correctly connected to their corresponding terminal on the thermostat. 
  4. In case you have a battery-operated thermostat, examine the batteries and change them if wanted. 
  5. The thermostat needs to be positioned away from drafts or direct daylight to get an correct studying.
  6. Test for grime and particles inside, and clear if wanted.

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5. Soiled Air Filters

In case your furnace air filters are soiled or clogged, they will limit airflow, inflicting your furnace to work more durable. This can lead to overheating and eventual failure of the unit. 


If the filters are clogged or broken, they need to get replaced. Altering your filters each two weeks and changing them each 3-4 months is really useful.

6. Leaking Ducts

Leaking ducts could cause the furnace to run inefficiently. The air that’s meant to be heated will escape as an alternative, leading to wasted vitality and excessive payments. 


One of the best ways to resolve this widespread furnace downside is to seal the ducts correctly. This may be carried out utilizing mastic or foil tape on prime of the cracks and gaps. You may also have knowledgeable HVAC technician examine and repair the leaks. In some instances, changing all the duct system could also be crucial.

7. Thermostat and Furnace Are Mismatched

In case you have put in a thermostat that’s incompatible together with your furnace, you’ll face working issues. Because of this, your furnace could overheat or underheat your own home.


  1. Test your thermostat handbook to seek out out if the furnace is appropriate with it or not. 
  2. If the improper sort was put in, change it with the right mannequin. 

8. Inadequate Warmth Output

Inadequate warmth output in a furnace is when it doesn’t produce sufficient warmth. Your furnace could cease producing warmth or blow cool air solely. This may occur for varied causes, a few of which will be taken care of at dwelling.


  1. Ensure the warmth registers are open.
  2. Test the thermostat settings for any attainable adjustments.
  3. Confirm that the furnace has energy and is working.

9. Furnace Biking Issues

The biking points in furnaces embody brief biking, when the furnace activates and off too usually, or over-cycling when the furnace runs longer than crucial. Over-cycling places further pressure on the furnace’s elements, resulting in elevated put on and tear. 


  1. Clear or change the air filter frequently.
  2. Test the thermostat settings and calibrate them if crucial.
  3. Study the burners for correct operation and clear them if crucial.
  4. Alter the blower pace to make sure correct air circulation.
  5. Guarantee ample return air provide.

Blower Parts Malfunctioning

10. Frayed Blower Belt

The blower belt is part of the furnace that helps its fan to run easily. Over time, it may well turn out to be frayed resulting from on a regular basis utilization or may slip from its place. In case your motor belt malfunctions, you’ll hear a high-pitched squealing noise.


It’s important to switch it as quickly as attainable. If the belt is left on this situation, it may well trigger the furnace to overheat and trigger additional injury. 

  1. Ensure to purchase the right dimension belt earlier than you begin the substitute course of. 
  2. To interchange the belt, you have to flip off the ability to the furnace.
  3. To entry the blower belt, you’ll have to take away the blower panel. Then use the wrench to loosen up the bolts and take away the outdated belt. 
  4. Put the brand new belt as a substitute, so it’s comfortable.
  5. Lastly, reinstall the entry panel and activate the ability to the furnace.

11. Worn-Out Ball Bearings

In terms of sustaining your furnace, one a part of the blower mechanism that ought to at all times be checked for issues is the set of ball bearings. They will develop put on and tear over time. They will additionally turn out to be broken if they don’t seem to be correctly put in. If there are points together with your furnace’s ball bearings, you’ll hear a scraping sound coming from the system.


Working your furnace whereas these bearings are failing will solely make issues worse, so flip off your system and make contact with your furnace technician to switch the ball bearings as quickly as attainable.

12. Broken Blower Capacitor

The capacitor is sort of a battery in your furnace that gives vitality for it to operate. If the capacitor goes haywire, then the motor will draw an excessive amount of energy from the circuit board to operate correctly. This may result in an overload that forces breaker journeys and even wire shorts.


Have an HVAC skilled take a look at the capacitor and examine the injury.

13. Noisy Furnace

In the event you hear unusual noises like pinging or popping, squealing, grinding, or rattling,  it’s almost definitely an indication of an underlying furnace downside. For example, a squeaking noise often signifies issues with the blower belt, whereas scraping noises level to broken blower bearings. Rattling noises in your furnace will be brought on by unfastened elements, worn-out bearings, clogged burners, or a cracked warmth exchanger.


  1. Test the blower belt for put on or injury. 
  2. Examine the blower housing and motor for any unfastened or broken elements. Tighten the unfastened screws and likewise oil the motor for lubrication. 
  3. Examine the warmth exchanger for any cracks or blockages. Name an HVAC technician if repairs are wanted. 
  4. Clear or change the filters, as a clog could also be making the noise.

Associated: Air Conditioner Noises: What Causes Them & How to Fix

14. Cracked Warmth Exchanger

The warmth exchanger separates the flame from the air. In the event you don’t sustain with the furnace upkeep or in case you set the temperature too excessive, the exchanger can crack. You’ll hear rattling noises if this occurs. 

This crack permits probably harmful fumes, reminiscent of carbon monoxide, to flee into the house as an alternative of being vented to the surface. This may create a probably hazardous state of affairs and needs to be addressed instantly.


Sadly, this isn’t one thing that may be carried out with out skilled help. You will have to have an HVAC particular person are available to examine the furnace and change the warmth exchanger if crucial. 

15. Fuel Valve Malfunction

A defective gasoline valve can result in varied points together with your furnace, together with inefficiency, extreme noise, and even security hazards. As well as, it may well trigger the furnace to not ignite or warmth correctly. This may be harmful as it may well result in a gasoline leak or an explosion.


  1. Flip off the electrical energy to the furnace.
  2. Find the gasoline valve and shut it off.
  3. Take away the entry panel from the furnace.
  4. Examine the gasoline valve for any seen indicators of harm.
  5. If the valve is broken, change the valve with a brand new one.
  6. Reattach the entry panel and switch the ability again on.
  7. Activate the gasoline valve and examine for any leaks.
  8. If there aren’t any leaks, reset the furnace and take a look at the system.

16. Soiled Burners

Soiled burners could cause a number of points for a furnace. First, they will scale back the furnace’s effectivity, inflicting it to run longer and value extra. As well as, soiled burners could cause the furnace to provide soot, which may accumulate within the ducts and vents and result in well being dangers. They will additionally trigger the furnace to overheat, severely damaging the system.


  1. Find the burners and clear them utilizing a vacuum cleaner to take away mud and particles.
  2. Subsequent, be sure that the burner ports are clear and unclogged. If the ports are clogged, use a wire brush or pipe cleaner to clear them.
  3. As soon as the burner ports are clear, use a compressed air canister to blow out any remaining particles.
  4. Test that the burner is adjusted accurately and that the flame is burning blue. If the flame isn’t burning blue, regulate the burner.

17. Burning Odor

You could discover a bizarre burning odor if you first flip in your furnace at first of winter. That is often resulting from layers of mud burning off because it heats up, and this odor ought to dissipate inside an hour. Nonetheless, if any sturdy odors persist for a couple of days, it signifies a significant issue.

A moldy odor signifies the expansion of mould or mildew contained in the furnace. A metallic or gasoline odor alerts a gasoline leakage, and in that case, instantly flip off the gasoline valve and name for skilled assist. Open all of the home windows and evacuate your own home. 

Associated: 6 Reasons Why Your HVAC Smells & The Best Solutions

18. Soiled Flame Sensor

A grimy flame sensor could cause a furnace to malfunction by interfering with the furnace’s capability to sense the presence of a flame. The flame sensor is a small probe close to a furnace’s burner. It acts as a security gadget to make sure the furnace is working accurately and isn’t producing harmful ranges of carbon monoxide. Nonetheless, when the flame sensor is soiled, it may well’t precisely sense the presence of a flame, ensuing within the furnace not working correctly or not working in any respect.


  1. Shut off the ability to the furnace.
  2.  Take away the flame sensor from the furnace.
  3. Use an emery fabric or metal wool to wash the sensor, eradicating any grime or particles.
  4. Dip the flame sensor in heat water and a gentle dish cleaning soap answer.
  5. Gently scrub the sensor with a gentle brush or fabric to take away any remaining grime.
  6.  Rinse the flame sensor with clear water and dry it with a gentle fabric.
  7. Reinstall the flame sensor and activate the furnace.

19. Water Pooling Across the Furnace

Excessive-efficiency furnaces have condensation pipes that may turn out to be clogged or develop a leak. This may trigger water to pool round a furnace. 


  1. Test the slope of the ground to guarantee that the ground across the furnace is sloping away from it in order that any water that accumulates close to it may well naturally drain away.
  2. Examine the condensate line from the furnace to make sure it’s not clogged and draining accurately.

  3. Set up a sump pump. If the water continues to be pooling across the furnace regardless of the above steps, it’s possible you’ll want to put in a sump pump to assist pump the water away from the furnace.

20. Clogged Exhaust and Consumption Vents

Clogged exhaust and consumption vents are widespread furnace issues. On this case, air received’t have the ability to circulation freely, inflicting the system to turn out to be inefficient and probably even break down. Clogged vents will be brought on by varied issues, together with grime, leaves, snow, or furnishings items positioned in entrance of the vents. 


  1. Test all the within vents for any obstruction which may be stopping warmth circulation. For instance, a furnishings piece or a curtain could impede the vents. Transfer them apart to repair the difficulty. 
  2. Go exterior and examine the exhaust vents for blockage. Search for corroded or rusted vents. If they’re broken, the furnace technician must be known as for a substitute. 
  3. Test for blockages reminiscent of leaves or ice if there isn’t a injury. Take out the leaves and clear the vents. If snow is obstructing the vents, shovel the ice after which clear them. 
  4. After cleansing the exterior blockages, examine the within of the vents and search for soot or particles. Clear the within with a brush or fabric piece if required. 

Often Requested Questions

Listed here are some widespread furnace issues FAQs that you just is likely to be trying a solution for:

  • Can an Outdated Furnace Trigger Well being Issues?

Sure, older furnaces could trigger well being issues because of the launch of pollutants into the air. For instance, poorly maintained furnaces produce carbon monoxide, which is a colorless and odorless gasoline that causes critical well being issues. Moreover, older furnaces could also be unable to filter out particles like mud, pollen, and pet dander which may end up in allergic reactions and bronchial asthma.

  • What Issues Can a Soiled Furnace Filter Trigger?

A grimy furnace filter could cause plenty of issues, together with an inefficient furnace, hot or cold spots, elevated vitality prices, poor indoor air quality, clogged and soiled air ducts, and a excessive danger of furnace breakdowns.

  • Do Excessive-Effectivity Furnaces Have Extra Issues?

Excessive-efficiency furnaces are designed to be extra dependable than conventional furnaces and have fewer restore points. They’re additionally extra vitality environment friendly, which may save you money on your heating bills.

  • What Can Trigger Issues With 2-Stage Furnaces?

Potential issues with two-stage furnaces embody a blocked condensate line, clogged air filter, defective flame sensor, low refrigerant ranges, defective strain change, and defective inducer motor. Moreover, points with the thermostat, reminiscent of incorrect wiring or an outdated, malfunctioning mannequin, could cause issues with two-stage furnaces.

  • Who to Name For Furnace Issues?

It’s best to contact an authorized HVAC technician or contractor to diagnose and restore any furnace points. Seek for one of the best HVAC technicians in your space and guide an appointment. 

When Do You Name an HVAC Technician?

In case you have the set of experience and an applicable toolkit, the directions above can assist you tackle a number of challenges highlighted above. If that’s not the case, you may positively DIY a couple of issues and depart sophisticated issues with an professional. DIY furnace issues can embody issues like changing air filters, cleansing elements, or checking for blockages. Points that may want an HVAC embody a damaged furnace fan, a malfunctioning thermostat, or a defective ignition system. If you’re not sure of the reason for the issue or don’t really feel comfy trying a restore, it’s at all times greatest to name an HVAC technician.

Listed here are a couple of points you may deal with your self and some that should be assigned to a technician.

DIY furnace issues:

  1. Changing the furnace filter.
  2. Cleansing the blower meeting.
  3. Checking {the electrical} connections.
  4. Testing the thermostat.

Name an HVAC technician:

  1. If the furnace isn’t igniting or not producing warmth.
  2. If the furnace is creating unusual noises or smells.
  3. If the furnace isn’t biking accurately.
  4. If the furnace is leaking or not working accurately.

Reclaim Your Consolation With A Furnace Restore

Furnaces are an integral a part of home heating systems. They’re accountable for offering the best temperature in winter, and if they don’t seem to be working correctly, it may well compromise effectivity in addition to your consolation. Frequent furnace issues embody blocked or soiled air filters, malfunctioning thermostats, defective blower motors, and leaking ducts, amongst many others. These furnace issues can result in spiked payments and uneven heating. 

Therefore, it’s crucial that when you discover any irregularity together with your furnace, you don’t brush it off. Relatively take motion for it as quickly as attainable. You by no means know it may be an indicator of one thing a lot worse brewing in your furnace. Attain the foundation of the issue and consider in case you can deal with the difficulty your self or require skilled help.

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