Rheem Flammable Vapor Sensor Reset Problem [5+ Easy Fixes]

Rheem flammable vapor sensor reset problem mainly occurs when the sensor constantly triggering by any gasoline or other flammable gas around the heater. Plus, incompatible resistance of the sensor or at times faulty FVS itself lead to the issue.

rheem flammable vapor sensor reset problem

Besides, the water heater unit overheats due to the blocked air combustion chamber and clogged flame arrestors. This trips off the FVS safety mechanism as well as an unsuccessful resetting attempt. 

Faulty gas control is also a major concerned fact when you encounter an FVS sensor reset problem with your Rheem water heater.

Dealing with this annoying issue will seem easy as long as you will check our complete guide including all well-proven solution procedures. 

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What is a Flammable Vapor (FV) Sensor? How Does It Work?

The water heater from selected models features a few essential safety mechanisms that are specially designed to prevent any catastrophic breakdown of the system.

flammable vapor (FV) sensor

A flammable vapor sensor is such safety category equipment installed at the bottom of some specific water heaters including the Rheem model.

This is basically a silicone-based sensor that helps to detect any fumes near the heater that has a higher chance to ignite.

After sensing the flammable vapor, it shuts down the complete heating system and prevents the ignition of that flammable vapor. 

Some quality FVS comes with better sensitivity which can identify the gasoline constituents in the air. During this typical gasoline discharge near the unit, the sensor activates and leads the system into a soft lockout. 

Note: You can also read how to fix Rheem water heater chamber sensor failure/9 flashes.

Principle Of Flammable Vapor Sensor Operation

The sensor mainly features silicon-based material which contains carbon particles in a solid state. In the presence of gasoline constituents in the immediate environment of the heater, the silicon starts expanding including the carbon particles. 

The magnitude of resistance increase depends on the gasoline vapor concentration. Now higher vapors concentration means a higher expansion of the silicon film, which changes the resistance of the sensor. 

As the resistance changes, the sensor gets tripped and then the entire unit shuts down to reduce the risk of catching fire from the flammable vapors.

Rheem Flammable Vapor Sensor Reset Problem [5 Reasons To Fix!]

Here, we are going to highlight 5 major reasons with all effective solutions to the FVS reset problem. So, without any ado, let’s begin the main discussion.

1. Rheem Flammable Vapor Sensor Lockout

As you have already learned that the FVS functions by changing its resistance. After sensing the presence of flammable vapor that may ignite, the sensor resistance increases. 

rheem flammable vapor sensor lockout

Here are some of the most common flammable vapors which trigger the FVS sensor and change its resistance:

  • Benzene
  • Isoprene
  • Kerosene
  • Ammonia or sewer gas
  • Mineral Spirits
  • Bleach
  • Paint
  • Methanol 

Due to designated changes in the resistance, the heater goes to soft lockout mode and turns off the heating system. In this mode, the gas stops operating and the pilot light shuts down which would stop heating the water. 

In this case, first, place the flammable substance away from the heater area. Then try to reset the FVS to take your water heater out of lockout mode. 

Here is the detailed guide on how you will reset the FVS lockout to turn back on the heater.

How To Reset Flammable Vapor Sensor On A Hot Water Heater

Certain Rheem water gas water heater models may feature 2 kinds of gas control valves. One is a white Rodgers Intelli-vent power vent control model and the other one is a Honeywell gas control-equipped model. 

The FVS resetting methods for these two models are far different. No worry!! We are going to explore the FVS resetting process for both types of gas valves.

i). White Rodgers Intelli-Vent PowerVent Control Equipped Models:

power vent control equipped models
Step 1:

First, unplug your Rheem water heater from the power connection. Leave your water heater unplugged for about 10-20 seconds. Then plug it back in again. You need to wait for another 5 seconds.

Step 2:

You will see arrows on the control valve. Press and hold both arrows together for 5 seconds. Keep pressing until the green LED blinks. When the green light blinks, enter a cheat code by pressing the arrows.

The code is: “Left, Right, Left, Left, Right, Left, Right, Right.”

That’s it!! The LEDs will light up, signifying the FV sensor is reset.

ii). Honeywell Gas Control Equipped Models:

You have Honeywell gas control, as shown in below picture, follow the below instructions to reset the FVS:

honeywell gas control equipped models
Step 1:

Start by disconnecting the power connection from the water heater. Wait for 10 seconds and then plug the unit back again.

Step 2:

Now, it’s time to reset the FVS. First, turn the pilot knob clockwise to the “Pilot” position first. Then, turn it counterclockwise to the “Very Hot” position. 

Rotate the knob back and forth from the “Pilot” to the “Very Hot” position. Repeat this attempt six times in 30 seconds.

The FVS has been reset, and your water heater should be out of lockout mode. 

2. FV Sensor Resistance Is Out Of Range

Most of the time, the FVS fails to prove well and still you may encounter the lockout issue. It is sure the faulty resistance setting on the sensor is now to be blamed.

A well-operating flammable vapor sensor resistance range should be between 3k ohms-48k ohms

Now you can check the resistance of your water heater FVS to know whether it is giving the recommended resistance reading or not.

How To Test the Flammable Vapor Sensor Of Rheem Water Heater

Go through the below steps to measure the resistance of the FVS on your Rheem water heater:

Step 1: Detach The FV Sensor

First, locate the FVS from the basement of your water heater. Remove the FV sensor from its bracket. Now, disconnect the wiring harness of the terminals at the sensor. 

locate the FVS

Step 2: Set The Multi-meter

It is ideal to use a multimeter to check the resistance of the sensor. First, set the reading to the ohms setting.

use a multi-meter

Then, attach the leads of the multi-meter with the two terminals of the FV sensor as shown in the picture. 

Step 3: Take Note Of The Resistance Reading

Now, start measuring the resistance of the FVS. If you find the resistance reading under 11k ohms or above 45k ohms, verify the FVS is defective. You have to replace the faulty FVS. See the following section!

3. Faulty Flammable Vapor Sensor

Once you have confirmed that the resistance of FVS is not at the recommended level, consider replacing the FVS as the better and safer option. 

Replacing the FVS is not tough and you can do it by yourself without any assistance from professional hands. Just follow the below DIY methods:

How To Replace Flammable Vapor Sensor From The Rheem Water Heater

Before installing, make sure that the installation area is free from flammable and other potential sensor-contaminating vapors. Once confirmed, proceed to the next steps: 

  • First, remove the outer cover door of the burner compartment of the heater. Then, remove the tap securing the FVS to the tank. Pull the sensor wiring harness from two terminals of the sensor cap.
  • After that, disconnect the faulty FVS from the connection. Take the new FV sensor and start installing it by connecting the new sensor to the wiring connections.
  • Next, push the sensor and wiring into the sensor cap and ensure it snaps or clicks into place. Last, reassemble the front burner compartment cover of your water heater. 

4. Rheem Water Heater Vapor Sensor Keeps Tripping

The FVS sensor keeps tripping is the most common problem of the Rheem water heater user deal with.  There are several factors that lead to the FV sensor keeps tripping constantly.

 Go through all the major viewpoints below, responsible for this issue:

i). Accumulation Of Dust

The Flame Arrestor or mostly known as a flame trap is the essential equipment of the unit, located under the water heater’s base. It is part of the Flammable Vapor which is used to escape the gas combustion chamber. 

accumulation of dust

As the arrestor is always accessible through the air intake opening, thus accumulation of lint, dirt, and oil is obvious. Due to clogging in the sensor, the trapped combustion gas increases the water heater’s internal temperature and triggers the sensor. 


You need to keep the arrestor always neat and clean to allow escape the combustion gas thoroughly from the heater. Take a non-metallic brush and periodically pull it to remove dust/debris from the bottom of the flame arrestor. You use can a vacuum as well for cleaning. 

ii). Detecting Volatile Constituents

The flammable vapor sensor is designed to detect volatile elements in the installation area. Like using a cleaning solution containing hydrocarbon solvents or placing oil-based paints near the heater. 

The FVS has a tripping point that will constantly be tripped from the higher exposure of such flammable segments.


  • Check whether there are any combustible materials nearer the heater. It will be better to place them far away from the unit. 
  • Then resetting the FVS should be your next course of action to get rid of the problem. We have already discussed the resetting process above in detail.
  • Thirdly, place your heater at least 18-20 inches off the ground. This is because the gas vapors are much denser than air and can’t lift up 18 inches from the ground.

iii). High-Temperature

High temperature is another major reason why the sensor keeps tripping. The FVS is very sensitive to ambient temperature. It is designed to operate well when the temperature is in a normal range. The higher temperature increases the resistance that trips off the sensor. 

See the table below to know about the absolute requirements for the FVS.

Element NameFlammable Vapor Sensor
Base Resistance @ 25°C7 to 25 KΩ
Trip Point50 KΩ
Operating Temperature Range0˚C to 65˚C (32˚F to 150˚F)
Humidity10% to 90% RH
Voltage5 VDC


First up, you need to inspect the combustion chamber to see where there is soot or dirt buildup that is creating blockages. If yes, vacuum out the combustion chamber and air filter to remove dust and lint.

 If still, the sensor is tripping, be sure it is faulty and you need to replace the defective FVS. 

5. Non-operation Gas Control Valve

Sometimes, the gas control valve of your Rheem water heater can be faulty, causing the flammable vapor sensor reset problem.

gas control valve

Here you might be resetting the FVS but it won’t prove well if the valve is worn out or damaged. Plus, it stops the heater from functioning properly. 

In this instance, the only solution is to replace the faulty gas control valve. Contact any certified plumber to replace the faulty gas valve.

But you can also do it by yourself as long as we have already explored some basic steps to replace the defective gas valve. Here you go!!

How To Replace Gas Control Valve On A Hot Water Heater

Follow the below instructions to replace the defective control valve from your Rheem water heater:

  • First, turn off your heater and also shut off the gas shut-off valve. Then, turn off the water supply. Open the drain valve to drain the remaining water from the tank. 
  • Now use a wrench to detach the gas supply line from the gas valve. Also, disconnect the valve adapter and burner assembly. Carefully, unplug all the connections going to the gas valve.
  • Remove the defective gas control valve using a wrench. When done, install the new gas control valve back in place and connect all the necessary attachments to the new valve. Finally, connect the power connection to the heater and open the gas supply.


How Do I Clean Flammable Vapor Sensor?

As an FVS features a high-sensitivity nature, thus proper maintenance is a must. Detach the FV sensor from the bottom or on the front and check for any contamination and dirt accumulation. If yes, clean it using a soft cloth.

Is there needed to install a flammable vapor sensor in my water heater?

Yes! Definitely!! If there are combustible constituents in the atmosphere that may ignite, the FVS trips off and prevents it from entering the chamber. Thus, this crucial safety element is needed in the light of ensuring a safe environment

Bottom Lines!

Throughout this article, we have discussed up to 5 of the most common reasons behind the flammable vapor sensor reset problem of your water heater. We are hopeful that this guide was an easy read for you to learn how to fix the flammable vapor sensor reset problem with ease. 

Still, if your problem has not been solved or having confusion at any point, then let us know in the comment box. We will try our best to solve the problem as soon as possible.

About William

William is the founder of Fireplacehubs.com. 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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