Furnace Troubleshooting Steps

Check Thermostat Settings And Power

If you’re piling on the blankets because your heat is out, check your thermostat first. This control center monitors your home’s temperature and tells the furnace when to kick in.

• Batteries: Replace the thermostat’s batteries if the display screen is dim or not responding.
• System mode: Make sure the thermostat is set to “Heat” and not “Cool,” “Fan,” or “Off.”
• Temperature: Set the desired temperature higher than the current room temperature.
• Programmed settings: Look for settings preventing the heat from turning on. For example, the heat may be programmed to switch off during the workday.

Inspect the Furnace Filter and Airflow

Air needs to flow freely so your HVAC system can warm your home reliably. Otherwise, your furnace may heat unevenly or turn off. Here are some common airflow problems:

• Furnace filters: Filters typically need changing every 2 to 3 months. Inspect filters monthly in the winter for optimal performance and replace them if debris has built up.
• Blocked vents: Inspect walls, floors, and ceilings to ensure nothing is obstructing the vent, and air can circulate. Curtains, furniture, and rugs can restrict airflow.

Look For Tripped Breakers or Shut-Off Switches

Power issues may also prevent your furnace from working. Investigate the following electrical issues:

• Tripped breakers: Check your home’s electrical panel. If the breaker to your furnace was tripped, reset it to restore power. It’s normal for a breaker to trip occasionally to prevent circuits from overloading, but your power shouldn’t shut down frequently. Ask a professional electrician to perform an electrical inspection if your circuit breaker keeps tripping.
• Furnace power switches: Your furnace should only be shut off in case of emergency or during servicing. Look for a furnace control on the wall next to the unit that looks like a light switch, and check that it hasn’t been turned off. The furnace will also shut off if the front panel is open, so give the door a push to make sure it’s secure.

Check Pilot Light or Ignition System Issues

Before your furnace can generate heat, it needs to start the combustion process. If there’s a problem with the pilot light or ignition system, the furnace won’t light and burn fuel.

• Older furnaces have a pilot light or standing flame. The pilot light may go out because of a draft or mechanical issue. Follow your manufacturer’s instructions to relight it.
• Newer furnaces have an electronic ignition system. You might hear clicking sounds if the igniter’s struggling to start or a bang that suggests gas build-up and delayed ignition. Your furnace might also start and stop frequently, which is a sign that the igniter isn’t staying on or a safety feature has kicked in.

Mechanical failure and gas-related problems can be dangerous, so call an HVAC contractor instead of trying to fix the furnace yourself.

Watch for Warning Signs that Require Professional Help

While you can troubleshoot basic furnace problems, some malfunctions require specialized knowledge. Contact a licensed professional if you notice:

• Gas odors or burning smells
• Black soot around the furnace
• Unusual banging, rattling, or scraping
• The furnace cycling off and on repeatedly
• The furnace failing to start

These signs can indicate a mechanical, electrical, or gas-related problem that’s risky to repair yourself. To prevent hazards such as gas leaks, fire, and electrical shock, leave the repairs to a professional.