Why Is My Furnace Not Turning On?

There’s nothing more frustrating than a furnace that refuses to turn on, especially when you’re counting on it to keep your home warm during Colorado’s colder months. Many furnace problems have common causes you may be able to troubleshoot. In this post, we’ll walk you through steps to fix these issues:

• Thermostat isn’t set correctly or isn’t working
• Furnace isn’t receiving power
• Clogged air filters
• Blocked or restricted airflow
• Pilot light or ignition sensor isn’t working

Let’s dive into troubleshooting tips to get your furnace running again.

The Thermostat Isn’t Set Correctly or Isn’t Working

If your furnace isn’t turning on, check your thermostat settings. Ensure it’s set to ​“heat” with the temperature above the current room temperature. A common mistake is setting the thermostat to ​“fan” mode, which only circulates air without heating it.

Next, verify your thermostat has power and try resetting it. If your thermostat takes batteries, replace them with new ones. Alternatively, if it’s hardwired, you may be unable to tell if it’s connected correctly and you’ll need to call a professional.

Thermostats that suddenly lose power even with fresh batteries, don’t respond to adjustments, or just flash even after being reset may have faulty components or wiring problems. You may need a new thermostat to restore proper furnace function.

The Furnace Isn’t Receiving Power

If there’s no noise from the furnace, air from the vents, or response when adjusting the thermostat, it could signal power loss. Always be cautious when troubleshooting electrical components. 

Open your main electrical panel to see if the furnace’s breaker has tripped. Try flipping it off and back on. If you have a fuse panel instead, see if the fuse has blown and needs replacement. 

Some furnaces plug into an electrical outlet with a switch that turns off the power. This switch may have been inadvertently turned off. Look for a switch near the furnace and turn it on to see if that restores power. 

If none of these tips work, you may need to call an expert for furnace repair. Be sure to call a professional if your furnace constantly trips the breaker or blows fuses. It might signal a more significant problem.

The Air Filters Are Clogged

Clogged air filters can prevent your furnace from running efficiently or even stop it from turning on. Dirty filters restrict airflow, potentially causing the furnace to overheat and shut down as a safety measure. Regularly changing your air filter helps prevent this issue.

Using high-quality filters is essential for maintaining efficiency and extending your furnace’s lifespan. Scheduling regular professional furnace maintenance also ensures it stays in top condition.

There’s Something Blocking or Restricting Airflow

Poor or restricted airflow can prevent your furnace from working correctly. Signs of airflow issues include weak or uneven heating throughout your home or unusual noises coming from your furnace.

Inspect your ductwork to make sure there’s no blockage or damage restricting airflow. Checking ductwork can be challenging. Consider calling a professional to handle inspections and routine duct cleaning to maintain efficient furnace operation.

The Pilot Light or Ignition Sensor Isn’t Working

A malfunctioning pilot light or ignition sensor could keep your furnace from turning on. For gas furnaces with traditional pilot lights, see if the flame has gone out. To safely relight a pilot:

For newer furnaces with electric ignition systems, you may need to reset the system to resolve the problem. Turn off the furnace, wait a few minutes, and turn it back on. Troubleshooting may also involve checking for error codes.

Call a professional for more complex ignition issues to ensure safety and compliance with regulations, especially if you notice repeated error codes or failures indicating a system malfunction.