When winter sets in, a working furnace is essential. If you turn up the thermostat and only feel cold air, it can be frustrating and concerning.
This guide will walk you through the most common reasons a furnace stops heating and how you can safely troubleshoot them before calling a professional.
Common Reasons Your Furnace Is Not Heating
Before you panic, there are a few simple things that might be causing your furnace to act up.
1. The Thermostat Settings Are Wrong
Sometimes the fix is as simple as checking the settings. Make sure your thermostat is set to “Heat” and not “Cool” or “Fan.” Also, check if the fan setting is on “Auto” rather than “On.” If it’s on “On,” the blower will run constantly, pushing unheated air even when the furnace isn’t firing.
2. A Clogged Air Filter
A dirty air filter restricts airflow, which can cause the furnace to overheat and shut down as a safety precaution. Check your filter monthly and replace it every 1-3 months.
3. The Pilot Light or Igniter Is Out
If you have an older furnace with a pilot light, check if it’s lit. If it’s out, follow the manufacturer’s instructions to relight it. If you have a modern furnace with an electronic igniter, it might be faulty and need replacement.
4. A Faulty Flame Sensor
The flame sensor is a safety device that detects if the gas is burning. If it gets coated in carbon buildup, it won’t detect the flame and will shut the furnace down. This is a common issue that requires a technician to clean or replace the sensor.
When to Call an HVAC Professional
While some issues can be resolved with basic maintenance, others require expert attention. Always prioritize safety.
If you smell gas, leave the house immediately and call your gas provider. If you hear loud banging, rattling, or grinding noises, shut the system down and call a licensed HVAC technician.
For more severe issues, it’s best to consult a professional to avoid damaging the system further. You can learn more about costs in our Furnace Repair Guide.
Next Step: If you’ve checked the basics and your furnace is still not working, don’t wait for the house to get cold. Find local HVAC help today.