Furnace Troubleshooting Tips for Common Problems

Furnaces are your home’s winter trooper. They keep all rooms toasty for you and your loved ones, eliminating cold spots in every nook and cranny. Since it’s the most worked appliance in the cold season, problems can prevent this workhorse from working as expected.

The last thing you want to happen is freezing your toes in the middle of the night. Here’s a furnace troubleshooting guide with easy-to-follow instructions for common issues. 

Furnace Not Heating Up 

Does your home suddenly feel cold? Your furnace must not have power. There are multiple reasons for this, so we’ve listed various troubleshooting furnace fixes.

Turn on the Furnace Switch 

Press the furnace switch near the heating component. If that doesn’t do anything, go to your home’s breaker box and ensure the master switch is on. 

Check the Thermostat 

If your furnace stops working, inspect your thermostat. Most models require battery replacement to continue running. For electronic units, see if the date and time displayed on the panel are correct. For smart thermostats, ensure they’re connected to the internet. 

Dust off debris from the thermostat’s surface and set its mode to heating. Crank up the device to activate the furnace. 

Related: Read All About Furnace Installation and Maintenance in This Guide

Working Furnace But Insufficient Heat 

Your furnace is on, but the indoor atmosphere still feels cold. Troubleshooting furnace components is key for this issue.

Replace Furnace Filter 

During the heating season, a furnace’s air filter collects dust and debris quickly. Leaving the dirty filter inside the system causes poor warm air delivery. That’s why you must replace or clean a clogged filter every 90 days; failure to do so may lead to irreparable damage.

Related: The Ultimate Seasonal HVAC Maintenance Guide for Homeowners

Unblock HVAC Grilles or Registers 

Grilles and registers draw stale air from rooms for heating. If these openings are blocked by debris build-up or furniture, there won’t be enough air to heat resulting in insufficient heating.

Seal Ductwork 

Leaky air ducts allow warm air to leave before dispersing in your home, causing unchanged cold temperatures. Sealing duct connections requires expert attention for accurate performance. Call a professional and let them inspect, insulate, and seal your ductwork to make your home and furnace more efficient. 

No Pilot Light 

A pilot light is a gas burner’s ignition source and could be one of the reasons your furnace isn’t working. If this doesn’t have a light, the furnace won’t run. Fix this issue by following the furnace troubleshooting steps below:

1. Ensure ample gas or propane supply. Contact your gas company for replacements and refills. 
2. Switch the gas valve to its off or closed position and let the gas dissipate for five to 10 minutes.
3. At the bottom of your unit, find the pilot light knob and turn it to its off position. Wait for a minute before moving the knob back to the on position. 

Important Note: Read your furnace’s manual guide for furnace troubleshooting instructions. Every model has different pilot light settings so ensure you do what’s right for your unit. 

Reigniting the pilot light yourself is fine, but we recommend asking a professional for help for safety reasons. If you smell gas during your attempt, leave the house and call HVAC technicians to fix the issue. There are no DIY furnace troubleshooting for gas leaks!

Furnace Blower Motor Turns On and Off Often 

The blower circulates air within the furnace unit and your house. It should run until the desired room temperature is met. If it keeps running, there could be multiple reasons why: a faulty limit switch, corroded flame sensor, or blocked ductwork, to name a few.

We suggest reading our guide on furnace blowers for a more detailed explanation. Learn the different reasons your blower turns on and off and the troubleshooting furnace solutions you could do.

Strange Noises Coming From Furnace 

Popping, clicking, and banging sounds are signs your furnace needs attention. Usually, these sounds mean a major problem that no DIY troubleshooting furnace solution can fix. Find out the different causes of a noisy furnace in the list below:

• Dry or rusted mechanical components
• Clogged air filter
• Debris build-up inside ductwork
• Loose or broken belt
• Loose furnace panels
• Worn-down furnace bearings

The sound alone isn’t enough to determine why your furnace is noisy. Calling a professional is the best troubleshooting furnace solution for this issue. They can inspect your furnace thoroughly and accurately identify the cause of the noise. 

Safety Switch Near Furnace Door Turned Off 

All furnaces come with a safety switch that stays on when the furnace door is closed. The switch goes off automatically when the door is opened or removed. 

What to do if the furnace stops working? Check the access door to see if it’s open. Push the door back into its opening to turn the safety switch back on. Doing so restores power to the furnace and allows it to operate as usual. 

Gas Furnace Troubleshooting Chart 

Save a copy of this furnace troubleshooting chart for fixes to each issue mentioned previously so you know what to do if the furnace stops working:

Troubleshooting Furnace With LG Home Comfort 

If none of our furnace troubleshooting tips worked, you may have a bigger problem. Call LG Home Comfort for a quick fix!

We offer emergency same-day troubleshooting furnace services, including diagnosis and repairs. Leave your furnace to us; our team will ensure it is up and running before temperatures drop. You won’t experience a cold winter when you choose Canada’s best HVAC service provider.

Our hotline is available 24/7. Call us at 1-866-530-5442 for emergencies or consultations.