Replaced Flame Sensor Still Not Working [7 Easy Solutions]

Replaced flame sensor still not working mainly because of the incorrect positioning of flame sensor in the flame, loose ground connection, burner and blower section’s defective plug-in connection.

Also, the loose connection between the flame sensor and wire, open pressure switch, faulty control board, and main circuit board and burner assembly’s faulty ground connections are responsible for it.

Anyway, by going through our, you will learn the reasons in detail and their solutions. So, let’s start…

Replaced Flame Sensor Still Not Working [7 Easy Solutions]

The major causes for which the changed flame sensor is still not working in your furnace and their effective solutions are the following:

1. Flame Sensor Is Not Positioned Properly in the Flame

Improper positioning of the flame sensor in the furnace’s flame is one of the main reasons for which the changed flame sensor is still not working.

The flame sensor can’t sense the hot blue flame within the furnace due to its improper positioning.

Therefore, if you fail to place the new sensor correctly on the burner assembly, it will not work even after replacing the old one.

The flame sensor is located in the furnace’s burner compartment just before the in-shot burners. Unfortunately, the sensor doesn’t work directly in touch with the flame, and it is designed to work slightly back from the stove’s flame.

So if you place your new flame sensor directly to the flame, it will obviously not work even after replacing it.


Ensure that the flame sensor in your furnace is appropriately positioned in the flame. Also, make sure that the sensor gets enough blue flame in the stove to sense.

Again, ensure that you didn’t place the new flame sensor directly in the flame. Instead, place it slightly away from the direct flame.

2. Loose Ground Connection

Losing the ground connection on the furnace’s transformer is another reason your flame sensor is not working. Ground connections play a significant role in the flame rectification circuit.

Thus still, after replacing your flame sensor, it will not work due to the ground fault. The causes of it are:

  • Corroded or damaged grounding wire
  • Melted ground wire
  • Incorrect wiring in the furnace or flame sensor placement
  • Ground fault inside the stove


Check all the ground connections correctly and ensure that all the connections are tight enough. The other simple fixing ways are:

  • Ensure a polished grounding point
  • Replace the damaged or corroded and melted grounding wire
  • During placing the new flame sensor, make sure it’s the correct wiring
  • Inspect the stove’s ground fault and repair it

3. Burner Section and Blower Section’s Faulty Plug-in Connection

A plug-in connection goes between the burner section and the blower section in your furnace. The improper plug-in connection between these two sections is another culprit for this issue.

Even after the flame sensor replacement, it is not working due to the connection malfunction. The causes of it are:

  • Burner and blower section’s loose connection
  • Damaged burner or blower section
  • The blower and burner section stops working because of the low thermostat setting
  • Excessive heat exposure to the burner and blower section


Inspect the plug-in connection between your furnace’s blower section and burner section and make sure these two are correctly connected. The other solutions are:

  • Ensure the tight plug-in connection between the furnace’s burner and blower section
  • Inspect the damaged blower or burner parts and replace it
  • Make appropriate thermostat settings. The settings should not be too low or too high
  • Ensure your furnace’s blower or burner is not facing excessive heat exposure

4. Flame Sensor and Wire’s Loose Connection

A loose connection between the flame sensor and furnace wire is one of the main reasons why your new flame sensor fails to work after the replacement. The factors responsible for it are:

  • Poor wiring within the furnace
  • The new flame sensor fails to adjust
  • Sensor’s broken connector


The easy fixing ways of the above issues are the following:

  • Inspect the replaced flame sensor and wire connection and ensure that they are tight enough
  • Ensure perfect wiring within your furnace
  • During the new flame sensor’s placement, make sure it is adjusting properly with the wiring
  • Replace the sensor’s broken connector

5. Open Pressure Switch

The new flame sensor in your furnace will not fix the previous flame outgoing issue due to the open pressure switch. The causes of it are:

  • Incorrect venting or blockage in the exhaust vent
  • Blocked fuel pipe
  • The clogged port on the pressure switch’s collection chamber


Carefully check your furnace’s pressure switch as current flows through it all the time. Fix the open pressure switch issue in the following ways:

  • Inspect and clean the furnace’s exhaust vent’s blockage and ensure correct venting
  • Clean the fuel pipe’s blockage
  • Remove the pressure switch collection chamber’s clogged port

6. Defective Control Board

If your furnace’s control board is defective, then the replaced new flame sensor will not work in it. The flame sensor fails to sense the hot blue flame due to the faulty control board.

The ignition sequence will not run longer or appropriately due to the defect in your furnace’s control board. The reasons for it are:

  • Faulty capacitors in the control board
  • Dirty or defective fuse
  • Defective blower motor
  • Loose wire connection
  • Temperature instability due to thermostat malfunction


Make sure your furnace’s control board is working correctly, and the board is showing Yellow LED. The yellow LED represents the flame sense condition, or there is a flame in the stove. The other solutions are:

  • Replace the control board’s faulty capacitors
  • Properly clean the dirty fuse
  • Tighten the loose wire connection
  • Replace the faulty blower motor and defective fuse
  • Inspect the malfunctioning thermostat and ensure the furnace is operating at a stable temperature

7. Faulty Ground Connection Of Main Circuit Board & Burner Assembly

The main circuit board and burner assembly’s defective ground connection is another reason why your replaced new flame sensor in the furnace doesn’t work. The concerning factors responsible for this problem are:

  • There is no ground conductor between the circuit board and the burner assembly
  • Faulty electrical connection between these two
  • Round (eyelet) terminations wiring between the main circuit board and burner
  • Dirty wire terminals and sheet metal surface
  • Loosen connection between terminals and assembly


The fixing ways of the above trouble are the following:

  • Between the furnace’s main circuit board and burner assembly, add a grounding conductor
  • Ensure and maintain the proper electrical connection between these two
  • Disconnect the round (eyelet) termination wiring
  • Use sandpaper to clean the dirty wire terminals and filthy sheet metal surface
  • Tighten the mainboard terminal and burner assembly’s connection


Why does my furnace flame sensor keep going out?

Your furnace flame sensor keeps going out mainly due to the lousy flame sensor, carbon build-up in the flame sensor, broken sensor, and sensor’s low tolerance of flame variations. Also, when the sensor misreads the carbon’s slightest coating, it shuts down.

Can you bypass a flame sensor?

Yes! You can do it. However, if you want to bypass your furnace’s flame sensor, you will be unable to light your stove manually. Also, before starting the flame sensor bypassing, ensure that all the safety measures are appropriately taken in place.

How do you trick a flame sensor?

The simple steps to trick the flame sensor are: first, shut off your furnace’s power and gas. Then remove the flame sensor. Next, use a smooth cloth to clean away the sensor’s corrosion and soot. Now again, start your stove by reinstalling the flame sensor correctly.

How does a furnace flame sensor work?

Your furnace’s flame sensor detects the flame’s presence within the stove. The metallic thin rod with a short length is called the sensor, and it creates electricity in a small amount in your furnace. So the sensor confirms that the stove’s fire is burning by creating electricity.


Now you know why your replaced flame sensor still not working in your furnace. If you face such trouble with your stove, detect the problems and fix them by yourself following the above-mentioned solutions.

Comment if you need any help fixing the issue. We’ll surely help you.

About William

William is the founder of He has real life practical skills in fixing smoker & heating appliance issues. He loves to share his knowledge & helps others in fixing their appliances & saving their money. William firmly believes that anyone can repair his or her unit with the correct guidance & knowledge. See more at about us.

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