While the cold nights in Louisiana may be far and few, you still want to rest assured that your furnace is functioning properly and ready to keep you warm on those chilly winter nights. When your furnace won’t turn on, Lee’s is here to help you troubleshoot it and make any necessary repairs to ensure your comfort throughout the winter.

Furnace that won’t turn on in the basement of a home in Louisiana.

Understanding and Troubleshooting Why Your Furnace Won’t Turn On

When your heating system fails to start, it can be frustrating and uncomfortable, especially during the colder months. There are several potential issues that may prevent your furnace from turning on, ranging from issues with your gas line to problems within the furnace itself. Whether you’re dealing with a minor glitch or a more complex furnace problem, troubleshooting the following issues will help you take appropriate action to restore warmth and comfort in your home.

Person setting thermostat to heat and lowering the temperature.

1: Check the Thermostat:

Your thermostat is the control center for your heating system, and if it’s not functioning correctly, it can prevent your furnace from turning on. Common issues include incorrect settings, a dead battery, or sensor obstructions.

  • Start by setting the thermostat to ‘Heat’ mode and increasing the temperature setting by at least 5 degrees above the current room temperature. 
  • Check if it has batteries – if so, replace them with fresh ones. 
  • Ensure that the thermostat is clean from dust and debris around its sensors. If you have a programmable thermostat, double-check the programmed schedule for accuracy.

2: Check Your Circuit Breakers:

Furnaces are typically connected to a dedicated circuit breaker or fuse. If this breaker trips or a fuse blows, it cuts off power so your furnace won’t turn on.

Locate the circuit breaker or fuse labeled for your furnace in the electrical panel. If it’s a circuit breaker, turn it off and then back on. For fuses, replace any blown ones with new ones of the same amperage. If the breaker keeps tripping or the fuses continue to blow, it may indicate an electrical issue and require professional attention.

Person replacing air filter in a furnace that won’t turn on.

3: Check Your Air Filters

Clogged or dirty air filters can impede airflow, reduce furnace efficiency, and lead to overheating, potentially causing the furnace to shut down for safety reasons.

Regularly check and replace your air filters every 1-3 months, depending on usage and filter type. Follow the manufacturer’s recommendations for your specific furnace model to ensure proper airflow and heating efficiency.

4: Check for an Issue With Your Gas Line

For gas furnaces, a problem with the gas line can prevent the furnace from igniting and heating your home. Issues may include a gas supply interruption, a closed gas valve, or a gas leak.

If your furnace won’t turn on, ensure the gas valve is in the ‘On’ position. If it was turned off, switch it back on. If you suspect a gas leak (smell gas or hear hissing), evacuate your home immediately, turn off the gas supply, and call a professional gas technician to address the issue safely.

5: Check the Drain Pan

Furnaces have drain pans to collect condensation and prevent water damage. If the drain pan is full or blocked, it can trigger a safety switch that prevents the furnace from turning on.

Inspect the drain pan for water accumulation. If it’s full, carefully empty it and ensure it’s positioned correctly. Check the drain line for clogs or obstructions and clear them if necessary. It’s important to address the underlying issue causing excessive condensation, such as a clogged condensate line or a malfunctioning humidifier, to prevent future problems.

6: Your Furnace Itself Could be the Problem

Sometimes, the furnace itself is the source of the issue. If your furnace won’t turn on, it could be due to technical failures, electrical problems, or malfunctioning components within the furnace.

In this case, it’s best to contact a professional HVAC technician at Lee’s for an in person inspection. One of our experts can perform a comprehensive inspection of your furnace, diagnose the specific issue, and recommend the necessary repairs or replacements.

7: Check if Something is Restricting Air Flow

Restricted airflow can lead to overheating and trigger safety mechanisms that shut down the furnace. It’s possible that your furnace won’t turn on due to blockages in the ducts or around the furnace.

Inspect all air vents and ducts in your home to ensure they are open and unobstructed. Remove any furniture, curtains, or debris that might be blocking airflow around the furnace. Keeping these areas clear will help maintain proper circulation and prevent overheating.

8: Check for a Faulty Ignition Sensor (Pilot Light)

Gas furnaces rely on a pilot light or electronic ignition system to ignite the gas. A faulty ignition sensor can prevent the furnace from lighting up.

For gas furnaces, follow the manufacturer’s instructions in your furnace’s manual to inspect and, if necessary, replace the ignition sensor or relight the pilot light. 

If your furnace won’t turn on after lighting the pilot light, and this is your first attempt at igniting your gas furnace for the current heating season, be patient. The ignition process may take some time initially. Factors such as the length of the gas line and the time it takes for fuel to reach the pilot light may slow down the initial lighting.

Lee’s HVAC technician making repairs to a furnace that won’t turn on.

How to Know When to Call a Professional

While some issues, such as dirty air filters, are easy to troubleshoot and fix yourself, others may require the expertise of a certified professional.

Additionally, if you’ve neglected regular maintenance or are unsure about the safety and efficiency of your furnace, it’s wise to schedule a visit with Lee’s for an inspection and repairs. Prompt professional attention in these situations ensures the safety, efficiency, and longevity of your heating system.

Regardless, the experienced technicians are prepared to identify why your furnace won’t turn on and make any necessary repairs to ensure your comfort and safety. Give us a call or book an appointment online today!

Leave a Reply