Troubleshooting Tips for Fixing a Broken Furnace

Nothing is more uncomfortable—or potentially hazardous—than finding yourself without heat during the coldest months. Before you endure the cold or call a professional, there are several troubleshooting steps you can take to possibly remedy a broken furnace. In this blog post, we’ll walk you through detailed troubleshooting tips for fixing common furnace issues, helping you understand when you can fix it yourself and when it’s time to call the experts at Upfront Plumbing Drains Heating & Air.

Signs of a Furnace Problem

Detecting problems early in your furnace can save you from more significant repairs down the line. Here are key signs that your furnace might be due for a check-up or repair:

Lack of Heat

If your furnace is not heating at all, it’s a clear indicator that something is wrong. This could be due to a variety of issues, from simple thermostat problems to more complex system failures.

Strange Noises

Any new or unusual sounds—such as banging, popping, rattling, or whining—coming from your furnace are not to be ignored. These noises could indicate loose parts, ignition problems, or even a failing motor.

Frequent Cycling

If your furnace is constantly turning on and off, this frequent cycling could point to a faulty thermostat, improper airflow, or other issues that are causing the furnace to overwork.

High Energy Bills

An unexpected spike in your energy bills can often be traced back to your furnace operating inefficiently. This could be due to a variety of factors including leaky ductwork, a dirty filter, or aging components that need adjustments or replacements.

Each of these signs can provide critical clues to underlying issues. Understanding them not only helps in troubleshooting potential problems but also in preventing future furnace failures. Recognizing these symptoms early and addressing them promptly can help maintain the longevity and efficiency of your heating system, ensuring it keeps you warm throughout the cold months.

Basic Furnace Troubleshooting Steps

Before you dive into more detailed inspections, start with these basic troubleshooting steps. These often resolve common issues and can save you time and possibly a service call.

1. Check the Thermostat

The thermostat is often the head of operations for your heating system. Incorrect settings or a malfunction can mimic a major furnace issue:

  • Make sure the thermostat is set to “heat” and that the desired temperature is set higher than the current room temperature.
  • If your thermostat is programmable, check that the time and date are correct, and the schedule is set appropriately for your current needs.
  • Replace the batteries if the display is non-responsive or dim. Old batteries are a common cause of thermostat malfunctions.
  • Look for any loose wires or corrosion in the battery compartment, which could affect functionality.

2. Examine Air Filters

A dirty air filter can lead to a multitude of furnace problems, including overheating and inefficient operation:

  • Turn off the power to the furnace for safety before inspecting the filter.
  • Remove the filter and hold it up to the light. If light doesn’t pass through easily, it’s time to replace or clean it, depending on the filter type.
  • Ensure the filter is inserted the correct way and fits securely. Incorrect installation can allow unfiltered air to circulate, increasing dust and allergens.

3. Inspect the Power Supply

Sometimes the solution is as simple as restoring power to the system:

  • Ensure that the furnace’s switch is turned on—sometimes these can accidentally be switched off.
  • Check your home’s main electrical panel for any tripped circuit breakers or blown fuses. Reset or replace as necessary.
  • For gas furnaces, ensure the gas valve is open to allow fuel to power the pilot light and burners.

4. Look at the Pilot Light and Ignition

Proper functioning of the pilot light or ignition is crucial for the furnace to operate:

  • For older models with a standing pilot, ensure the pilot light is lit. If it goes out, follow the manufacturer’s instructions to re-light it safely.
  • For newer models with electronic ignition, if the furnace fails to ignite, this system may need to be reset according to the manufacturer’s instructions.

Intermediate Troubleshooting Tips

If the basic steps don’t resolve the issue, you may need to look into more specific problems that require a bit more expertise.

1. Check the Gas Supply

A disrupted gas supply can prevent your furnace from operating:

  • Verify that the gas supply valve leading to the furnace is fully open.
  • Use a soap solution over the line; bubbling indicates a leak that needs professional repair.

2. Assess the Blower Motor

A non-functional blower motor can stop the furnace from circulating hot air:

  • Listen for any abnormal noises from the motor. A humming without turning could indicate a faulty capacitor.
  • Check the motor’s vents for any obstructions or dust accumulation.

3. Examine the Heat Exchanger

The heat exchanger is essential for heating the air without introducing combustion products to the air stream:

  • Inspect for any signs of visible cracks or rust, which could lead to dangerous carbon monoxide leaks.
  • Smell for odd odors emitting from the furnace or an unusual amount of condensation on windows or other cold surfaces inside your home, which can be signs of a faulty heat exchanger.

4. Flame Sensor and Burners

A dirty flame sensor or clogged burners can affect furnace operation:

  • Carefully clean the flame sensor with a soft cloth to remove soot and ensure it can properly detect the flame.
  • Inspect the burners for any dirt or debris that could obstruct the gas flow and clean carefully as per the manufacturer’s instructions.

When to Call a Professional

While many furnace issues can be addressed with DIY troubleshooting, certain problems require the expertise of a professional. It is important to recognize when a situation is beyond your capabilities, as incorrect handling can lead to further damage or pose serious safety risks. 

You should call a professional if the furnace still does not operate properly after you have performed basic troubleshooting. This includes persistent strange noises, which could signify deeper mechanical issues, or a continuous lack of heat despite your best efforts. If you detect the smell of gas or any other chemical odors, vacate your home immediately and contact emergency services followed by professional furnace repair services, as this could indicate a dangerous leak. 

Additionally, if you observe that your furnace is short-cycling—turning off and on more frequently than normal without any discernible reason—it’s time to consult with a technician who can diagnose and resolve underlying issues that are not apparent to the untrained eye. Finally, repairs involving gas lines, electrical connections, and the internal components of the furnace typically require professional skills and tools, along with adherence to safety codes and regulations that protect your home and family.

Preventative Maintenance

Maintaining your furnace regularly is the best way to ensure it operates efficiently and lasts through its intended lifespan without frequent breakdowns. Regular professional inspections are crucial, especially just before the heating season begins, to ensure that your system is problem-free and ready to perform. 

During these inspections, a technician can identify and fix minor issues before they turn into major problems. Keeping the area around your furnace clean and free from debris also helps to prevent system inefficiencies and potential fire hazards. It is also beneficial to keep an eye on your furnace’s performance throughout the heating season. 

If you notice any decline in efficiency or effectiveness, it may be time for a check-up. Additionally, upgrading aging parts, such as thermostats or specific furnace components, can significantly improve your system’s efficiency and reduce the likelihood of failures. Regular cleaning of air ducts and vents also contributes to better airflow and cleaner air, which not only helps your furnace run better but improves the air quality in your home.


Navigating the challenges of a broken furnace can be daunting, especially during the cold winter months when you rely on your heating system the most. By following the troubleshooting tips outlined in this guide, you can address many common furnace issues on your own, potentially saving time and money. However, it’s important to recognize your limits and understand when a problem is beyond DIY fixes. Calling in professionals like those at Upfront Plumbing Drains Heating & Air is crucial when you encounter complex issues, detect safety hazards, or if your troubleshooting attempts don’t resolve the problems.

Regular maintenance is key to prolonging the life of your furnace and ensuring it runs efficiently. By scheduling annual inspections and performing routine care, you can prevent many problems from ever occurring. Remember, the goal is not just to fix your furnace when it breaks down but to maintain it in a way that prevents future issues.

Whether you tackle furnace repairs yourself or decide to call the experts, being informed is your first line of defense against the winter chill. Stay warm, stay safe, and remember that help from experienced professionals is just a phone call away whenever you need it.

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