March 8, 2022

Because furnaces use natural gas or sustain periods of high heat, safety components are a vital part of their design. When functioning normally, they’ll keep the furnace from leaking gas or running for too long. One of these safety components is called the flame sensor, and it’s responsible for ensuring that the gas has been properly ignited.

If the flame sensor isn’t working correctly, your furnace may continue to allow gas to flow. This could lead to a gas leak, something every homeowner should avoid. Sometimes the problem can be resolved with a thorough cleaning, while damage or component failure could require flame sensor replacement. Let’s review possible reasons the flame sensor isn’t working and what you can do to keep heat flowing safely.

What is the Furnace Flame Sensor?

As we mentioned earlier, the flame sensor is a safety component designed to verify the presence of the ignition heat furnaces need to work properly. This could be a hot surface ignitor or an actual spark, so long as it ignites the natural gas. The sensor will continue to detect the heat as the furnace runs through a heating cycle, ensuring a steady flow of gas. Once the furnace is finished with its heating cycle, the flame sensor detects the drop in temperature and shuts the gas valve.

The flame sensor needs a clean surface to properly detect the heat within the furnace. While natural gas itself burns very cleanly, small amounts of dust and grime can gradually accumulate. If the sensor becomes dirty enough, it may not consistently detect the flame. This is why cleaning the sensor regularly is an important part of furnace maintenance.

But what if the sensor is still experiencing intermittent problems, even though it’s clean? The sensor could be damaged or malfunctioning, which will affect your furnace’s ability to operate safely.

Signs You May Need Furnace Flame Sensor Replacement

There are a number of signs that could suggest a problem with the furnace’s flame sensor. Some are noticeable on the flame sensor itself while others manifest as problems with how the furnace actually runs.

Checking the Flame Sensor Itself

  • Look for missing pieces or cracks in the sensor’s insulation, usually made of porcelain. This durable material protects the rest of the sensor from the furnace’s high heat.
  • When a technician is present, they can test the electrical resistance of the flame sensor. They’ll clean the sensor if it’s dirty and record the amp reading. If it’s lower than it should be, there could be a problem and the technician should start formal diagnostics.

Problems with How the Furnace Runs

  • Sometimes the gas won’t stay lit, turning the furnace off right after it started up. While this means the sensor is still performing its function as a safety component, it doesn’t make the problem any less frustrating. This problem is often known as short cycling and can add strain to many other key components.
  • Does the furnace sound like it’s running despite the lack of heat? A faulty furnace sensor may incorrectly detect the “proper” temperature, preventing the gas valve from shutting off. This could lead to dangerous quantities of gas building up inside your HVAC system or even your home itself.

While a damaged or malfunctioning flame sensor is a problem, the replacement process is pretty straightforward. Another benefit of routine furnace maintenance is it gives the technician an opportunity to examine the flame sensor and decide if it should be replaced.

Here’s What Furnace Flame Sensor Replacement Costs

Experienced technicians can quickly swap out the broken flame sensor for a new one. There are different models to choose from, which will influence the job’s total cost. You can expect to spend anywhere between $100 to $500. Older models may require sensors that are now difficult to find, which can complicate the process. In fact, you might be better off upgrading your heating entirely with new furnace installation.

While the average life span of a flame sensor is about five years, many technicians recommend replacing the flame sensor a little more often at every two to three years. This schedule helps ensure that the flame sensor is always in good condition and not causing problems with the gas supply.

Trust AC Mechanical for Safe, Efficient Flame Sensor Replacement

If you live in and around Cheyenne, call AC Mechanical for prompt and professional furnace services including flame sensor replacement. We’ll make sure it’s handled correctly, giving your furnace everything it needs for energy-efficient heating. Give us a call at 307-778-0515 if you think your flame sensor isn’t working the way it should.

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