What is A Furnace Flame Sensor and Why Is It Important?

The furnace that helps keep your home warm during the winters is made up of a variety of components. The smooth and proper functioning of all of these components is important to ensure that the furnace works right. If even a small component goes awry, your furnace may not work as it should.

One such small component is a furnace heat sensor, or furnace flame sensor. This is a small part, in the shape of a thin metallic rod, which is situated at the burner assembly of the furnace. Despite its humble appearance, this sensor performs a critically important job.

What Does a Furnace Flame Sensor Do?

As its name suggests, the basic task of a furnace is to detect whether or not a flame is burning in the furnace’s burner assembly. When the flame goes out, the sensor detects this. It then transmits an electrical signal to the controller. The signal tells the controller that a flame is no longer available to utilize the gas that is being supplied. In response to this signal, the controller shuts down the gas supply as well.

Importance of the Furnace Flame Sensor

The flame sensor is immensely important for the safe and proper functioning of the furnace. As noted above, the sensor detects when a flame goes out. It then alerts the controller to shut down gas supply. When the sensor malfunctions, the furnace continues supplying gas even when the flame is out. This can result in a fatal buildup of monoxide inside a room or closed space. In other words, the absence or malfunction of this sensor can pose a direct risk to your life and those of your family.

Furnace operation can produce poisonous carbon monoxide which is otherwise odorless and invisible. So it is virtually impossible to detect in time. The flame sensor does the sensing for you by shutting down gas supply in time to prevent precisely the buildup of unconsumed gas.

Given its critical importance, it is important to identify and resolve any furnace heat sensor failures in time. Here are some common signs you can use to detect problems with the sensor.

Common Signs of Failure

You can detect many telltale signs on your furnace that indicate that it has a flame sensor problem. Common signs that indicate the failure or malfunction of the sensor include:

  • The furnace lights up briefly but then turns off only after a few seconds.
  • The porcelain adjoining the flame sensor is cracked or visibly damaged in any other way.
  • The flame sensor is visibly corroded or has become darkened with soot.

When you are looking about the furnace for these signs, make sure you shut down the electrical and gas supplies to the unit. This helps ensure your safety during the inspection.

In many cases, the sensor no longer functions properly simply because of the carbon buildup, detectable as black soot. The good news is that when this is the case, you can simply clean up the sensor to restore it to its proper functioning. However, if the sensor has gone wrong for another reason, you will likely need to have it replaced.

Cleaning the Flame Sensor

Cleaning the flame sensor is a rather simple and easy task. Before you try your hands at it, make sure you have cut off the electrical power and gas supply to the unit.

You can find the sensor in the burner assembly, usually located in the rear of the furnace. The sensor is the metallic rod that is positioned directly in the path of the burner. The rod is typically attached to the unit with screws.

Use a screwdriver to undo the screws and detach the sensor. Then use a simple sandpaper to gently rub off carbon soot, dirt, and any other debris that has accumulated on the metal rod. During this process, care must be taken not to rub too hard or permanent damage to the rod may result.

Once you are done with cleaning the rod, simply screw it back in the burner assembly. Then restore power and gas supply to the unit and see if the furnace is working properly.

Hiring Experienced Greenville Heating and Air Experts

When the flame sensor in your furnace needs a simply cleaning, you can take a DIY approach. However, if another problem ails the sensor, you will likely need professional help. Here at General Air, we offer a comprehensive range of furnace installation, repair and maintenance services. Call us today to hire our services, get a free estimate, or simply consult our experts.

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