The sudden silence of a non-responsive furnace can send chills down your spine. Cold house and chattering teeth aside, a malfunctioning furnace can lead to costly damage from frozen and burst pipes. A furnace’s refusal to turn on may be due to something simple, such as a tripped circuit breaker or blown fuse. On the other hand, it could be more complicated and require professional repair. Either way, it’s important to embark on a troubleshooting journey to identify and address the underlying issues quickly.

Here are some of the most common reasons why a furnace may not turn on as well as steps to remedy the situation and get your home warm and toasty again.

Thermostat Woes

The thermostat acts as the maestro orchestrating your furnace’s performance. If the thermostat is not set correctly, lacks power, or has faulty wiring, your furnace won’t receive the signal to start. Begin by checking the thermostat settings, ensuring it’s set to “heat” and the desired temperature. Replace batteries if needed and inspect for loose or corroded wires.

Power Supply Problems

Ensure your furnace is receiving power. Check the circuit breaker labeled for the furnace in your electrical panel – if it’s tripped, reset it. If the furnace has a separate power switch, confirm it’s in the “on” position. Inspect power cords for damage and contact a licensed contractor if you notice any visible issues.

Dirty or Clogged Air Filter

A clogged or dirty air filter can hinder airflow, causing the furnace to overheat and trigger a safety shutdown. Inspect the air filter and replace it if it appears dirty. And in the future, change your air filter every 8 weeks or as recommend by the manufacturer. Regularly changing filters is crucial for maintaining optimal furnace performance.

Ignition System Issues

For gas furnaces, ignition problems can prevent the burners from lighting. Listen for clicking sounds during ignition attempts. If you don’t hear clicking, it may indicate a faulty ignition system. This could be due to a malfunctioning pilot light, ignition control module, or thermocouple. Consult a professional HVAC technician to diagnose and address these issues.

Faulty Pilot Light

If you have an older gas furnace with a pilot light, check that the flame is lit. A pilot light that goes out frequently may indicate a thermocouple problem. Follow the manufacturer’s instructions to relight the pilot light, and if it won’t stay lit, contact and HVAC pro for assistance.

Blocked Vents and Registers

Blocked or closed vents and registers can restrict airflow, causing the furnace to overheat and shut down. Ensure that all vents and registers are open and unobstructed to allow proper airflow. This simple step can resolve issues related to overheating.

Gas Supply Issues

For gas furnaces, a disruption in the gas supply can prevent ignition. Check other gas appliances to see if they’re working. If they aren’t, contact your gas provider. If they are, there may be a problem with the gas valve or supply line to the furnace, requiring professional attention.

Safety Switch Activation

Modern furnaces are equipped with safety features that trigger shutdowns in response to potential hazards. Examine the safety switch to ensure it hasn’t been activated. If it has, you may be able to reset it depending on the reason it was triggered in the first place. If you experienced a loss of power, you may need to reset the furnace once power has been restored. However, when in doubt, it’s best to contact a professional.

Thermocouple Troubles

The thermocouple is a safety device that senses the pilot light’s heat. If the pilot light is extinguished, the thermocouple shuts off the gas supply to prevent gas leaks. A faulty thermocouple may incorrectly sense the pilot light’s status, preventing the furnace from turning on.

When your furnace remains stubbornly silent, a little troubleshooting can help uncover the root cause and provide an easy fix. However, if your efforts prove fruitless or you’re not comfortable with the DIY approach, it’s time to contact Correct Temp. Our team of home comfort experts has the tools and expertise to restore warmth to your home quickly and keep your heating system running smoothly.