How to Clean the RHEEM Furnace Flame Sensor

Posted by: Mas Broto
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How To Clean The Rheem Furnace Flame Sensor

If your RHEEM furnace flame sensor gets dirty, the furnace won’t function properly. If you find that your furnace fires up, but shuts down after that, then chances are you’ve got a dirty sensor. Keeping the furnace flame sensor clean is a simple process when you follow our guide here.

A basic understanding of how your furnace works and where the part is located is a great idea for safety and troubleshooting. This article will help you identify the RHEEM furnace flame sensor on your furnace is and where the sensor is located. We will also detail what you need to know about keeping this part clean and why it is crucial.

What Is a Furnace Flame Sensor

The flame sensor is an essential furnace part located at the burner assembly. It’s a thin, usually bent metallic rod that sits in front of the pilot light inside the furnace. It is a necessary safety feature of your furnace.

A furnace flame sensor does what it says literally- to sense the flame. It makes sure there is fire once the furnace starts. In the absence of fire, the flame sensor sends a signal to shut off the gas or fuel valve to prevent dangerous gas build-up that can cause an explosion.

Signs of a Bad Furnace Flame Sensor

Sometimes, your furnace flame sensor can go defective and damaged. If you’re in doubt if it is your flame sensor that is acting up and causes troubles to your unit, check out these common signs of a faulty flame sensor:

  • Furnace turns on then off after a few seconds
  • Flame Sensor appears to be corroded or dirty
  • The porcelain on the sensor is cracked

Either of the three signs will cause your furnace to operate in short cycles- meaning, it will turn on then off in a few seconds. This happens because a dirty or damaged flame sensor won’t sense the presence of heat and will command the furnace to shut down. This can leave your home without heat in a cold season which can be very annoying.

RHEEM Furnace Flame Sensor Location

Before we go through the steps to clean the furnace flame sensor, let’s first locate the flame sensor inside your furnace.

  1. Remove the furnace cover. Remove the screws or knobs that hold the furnace cover in place. Rheem furnace flame sensor location is directly in front of you when you remove the access cover.
  2. Look at the burner assembly. The flame sensor is mounted just outside the burner assembly with wire/s attachment. The sensor sticks up through the housing and into the area where the flame is burning. It is a thin metal rod mounted by porcelain insulation on the other end.

How to Clean the Flame Sensor on RHEEM Furnace

Tools You Need:

  1. 1/4″ hex driver or wrench
  2. Small piece of light grit sandpaper, steel wool, or emery cloth
  3. Dry, clean paper towel

Step-by-step guide on how to clean RHEEM furnace flame sensor:

  • Shut off electrical power to your furnace
    You can switch it off through the toggle switch on/near your furnace or through its dedicated circuit breaker box in the absence of a control.
  • Locate the flame sensor
    Locate the flame sensor at the back of the furnace and in the path of the burner.
  • Remove the hex screws.
    The flame sensors are typically kept in place by one or two ¼” hex head screws.
  • Slide the flame sensor out
    Gently pull the sensors out from the burner bracket or assembly.
  • Detach the connected wires
    For some RHEEM furnace models, you may have to detach the wires connecting to the sensor to clean it well. This is unnecessary, but detaching the wires will give you ample space and flexibility to clean the sensor later on.
  • Visually check through the flame sensor.
    • If soot, corrosion and carbon build-up is visible, your furnace flame sensor just needs cleaning. This happens very commonly. The good news is that cleaning a furnace flame sensor is very easy. It can be done anytime with tools that are easily available at your home.
      Rub the probe with emery cloth or fine steel wool to remove carbon deposits. Before you start cleaning it, the probe will probably have a dull blackish color, and when you’re done, it should have a shiny silver hue. 
    • If there is/are visible crack/s on the porcelain insulation or obvious damage, the sensor must be replaced.
      Replacing your flame sensor is not a difficult task. First, simply redo the above steps– shut the furnace and gas valve off, remove the flame sensor from the assembly and detach the wires. Then, skipping the cleaning part, proceed by mounting the new furnace flame sensor by doing the above steps now in reverse.
  • Check if the problem persists.
    Once a clean/ new furnace flame sensor is remounted, check if the furnace now works properly. Next, turn the power and the gas valve on and see if the furnace stays on for at least one power cycle.

Where To Buy RHEEM Furnace Flame Sensors

In replacing your flame sensor, you have to make sure to purchase the correct part replacement. Again, local HVAC Shops is the way to go. Various local HVAC providers mostly have flame sensors available.

If you’re unsure which part to get, check your unit’s information inside the access panel. Go with your brand, model and serial number so they can suggest the best match for your unit.

How Much is the Cost of Furnace Flame Sensor Repair and Replacement

DIY repair and replacement.
If a dirty flame sensor is the only issue, all you need is light grit sandpaper, steel wool, or emery cloth which will cost you less than $5.

For replacement, buying a new flame sensor will cost you less than $10 to $100 depending on your unit model and if you’ll get an OEM or a universal part. However, most flame sensors cost $30 – $50 in the market.

Professional repair and replacement.
If this is the case, you have to pay the furnace repair company’s minimum service fees that go around $65 – $150. Plus, the cost of your new flame sensor, if it needs replacement, is less than $10 to $100.


Thus, it is very much economical to do your furnace flame sensor repair and replacement yourself. Besides, we have already walked you through the steps, and it is not a difficult job at all.

If DIY is not your thing, the thought of cleaning your RHEEM furnace flame sensor might sound intimidating. Thankfully, you can schedule a qualified technician to perform regular furnace maintenance on your unit. In addition, consider booking a yearly appointment with your local HVAC technicians to help ensure that your furnace is ready to perform all winter long.

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Mas Broto

Have been in the heating and air conditioning (HVAC) industry for over 20 years. He is person that will grow and thrive to learn more about the HVAC industry throughout his career. Mas Broto is also a blogger, who's dedicated to bringing you the best knowledge to get ahead in the game of life.

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