What Exactly Is a Flame Sensor?

Before diagnosing a faulty flame sensor, it's important to understand what this component does. The flame sensor is a safety feature commonly used in modern gas furnaces. Its primary role is to ensure the gas being supplied to the furnace is igniting properly. It detects whether the flame is burning and communicates this information to the control board. If the flame sensor doesn’t detect a flame, it will immediately shut down the gas valve to prevent gas buildup and the risk of a fire or explosion. It acts as the furnace’s “fail-safe” mechanism, so you can avoid potentially dangerous situations. With HVAC systems, this sensor works in conjunction with other safety mechanisms to make sure that your furnace operates efficiently and safely. If you notice issues with your heating system, such as it frequently shutting off, it may be time to contact an HVAC specialist in Redwood City or seek furnace repair.

Flame Sensor or Thermocouple

You may have heard the terms "flame sensor" and "thermocouple" thrown around when it comes to furnace maintenance, but these components are not the same thing. While both are essential for the safe operation of gas furnaces, they serve different purposes and are found in different types of furnaces.

• Flame Sensor: Typically found in newer furnaces, the flame sensor’s main function is to detect whether the burner flame is present. It signals the control board to keep the gas valve open as long as a flame is detected.
• Thermocouple: This component is often found in older furnaces and operates as a temperature-sensitive device. It creates an electrical current that keeps the gas valve open as long as it senses the heat from the pilot light. If the pilot light goes out, then the thermocouple cuts off the gas supply.

If your furnace has a pilot light, it’s likely you’ll need a thermocouple. In contrast, newer furnaces with electronic ignitions use flame sensors. Identifying which one your furnace uses can help an HVAC company technician quickly diagnose the problem.

How to Tell if Your Flame Sensor is Failing

A malfunctioning flame sensor can lead to several noticeable problems. Ignoring these signs may lead to larger issues that require furnace repair in Carmichael or even heating replacement. Here are eight common indicators that your flame sensor may be on the fritz:

• Furnace Cycles On and Off: If a furnace starts cycling off and on frequently, this could indicate a dirty or malfunctioning flame sensor. The sensor might not be detecting the flame correctly, causing the furnace to shut down prematurely.
• Furnace Won't Stay On: If the furnace starts but turns off after just a few seconds or minutes, the flame sensor might not be sending the right signal to the control board, which causes the system to shut down for safety reasons.
• Furnace Ignites But Quickly Shuts Off: Similar to short cycling, this is another indication that the flame sensor isn’t doing its job. If the sensor isn’t detecting a flame, the furnace will shut off for safety.
• Yellow or Irregular Flame: A healthy flame should be blue. If you see that the flame in your furnace is glowing yellow or is inconsistent, this could point to incomplete combustion, which might affect how the flame sensor works.
• Soot Build-Up on the Flame Sensor: Visible dirt or soot on the flame sensor is a sure sign that it needs cleaning. A dirty sensor won’t function properly, even if it's not technically broken.
• Unusually High Gas Bills: A malfunctioning flame sensor can cause your furnace to become inefficient, which may lead to higher-than-usual gas consumption.
• Carbon Monoxide Leaks: If the flame sensor isn't doing its job, gas could accumulate in the furnace and eventually leak, causing dangerous carbon monoxide levels in your home.
• Error Code on Furnace Control Panel: Many modern furnaces have control panels that display error codes. If your furnace is throwing a flame sensor-related error code, it’s time to call an HVAC specialist.

When to Consider Replacing Your Flame Sensor

While some flame sensor issues can be resolved by cleaning the sensor, there are instances when replacement is the best course of action. So, when should you opt for a replacement?

• Excessive Corrosion or Damage: Over time, flame sensors can corrode or become damaged due to normal wear and tear. If your sensor is visibly corroded or damaged, replacing it is a better option than attempting to clean it.
• Recurring Issues: If you've cleaned your flame sensor multiple times, but your furnace continues to act up, it’s probably time for a replacement. Continuously short cycling or not staying lit are red flags that the sensor has failed.
• Sensor Age: Flame sensors generally have a lifespan of 5 to 10 years. If your sensor is nearing the end of its life, it’s wise to replace it rather than wait for it to fail completely.
• Multiple Furnace Repairs: If you've had several furnace repairs recently and the flame sensor seems to be a recurring issue, a proactive replacement might prevent future problems.

When replacing your flame sensor, make sure you have a qualified HVAC specialist or technician handle the job. Although replacing a flame sensor is not the most complicated of tasks, ensuring it’s done correctly is essential to the safe operation of your furnace.

Rooter Hero Plumbing & Air is Here to Help

Dealing with furnace issues can be frustrating, but identifying a faulty flame sensor early on can save you a lot of trouble. If you're experiencing any of the signs mentioned above or suspect that your flame sensor might be bad, get in touch with an HVAC company like Rooter Hero Plumbing & Air. Whether it’s routine maintenance, furnace repair, or even a full heating replacement, we’re here to help. Contact us to schedule an inspection.