Rheem Water Heater Chamber Sensor Failure/9 Flashes [Solved]

Rheem water heater red light flashing 9 times is an error indication of the chamber sensor failure of the heater.

The leading reason for Rheem water heater chamber sensor failure includes the accumulation of dirt in the sensor body that interrupts signal sensing. Or, the chamber sensor may be defective due to the wrong resistance. 

rheem water heater chamber sensor failure

Besides, the heater triggers the ‘chamber sensor failure’ error code because of the flammable vapor sensor malfunctioning.

When it detects flammable vapor, it causes a soft lockout. Also, due to incorrect resistance, the FVS will stop working and need replacement. 

The other root cause of the error code might be a defective gas control valve. We need to test each suspected element and replace the faulty ones. 

Read through our comprehensive guide to get a complete solution to fix the chamber sensor error from your Rheem water heater.

Rheem Water Heater Red Light Flashing 9 Times [Solved]

Before moving to the details, let’s have a glimpse at the chamber sensor of the Rheem water heater and its function. 

What Is Chamber Sensor On Rheem Water Heater

In every Rheem water heater, there is a flame sensor which is referred to as an essential part of the heater ignition system. The flame sensor is located inside the combustion chamber. Thus, it is named the chamber sensor in the water heater. 

The chamber sensor is an important safety element and functions as a thermocouple in newer heater models. The main function of the sensor is to convert the heat from a burning flame into a small electrical current. This current will work as a switch to open the gas supply valve and allow gas to flow into the burner.

Note: You can also read how to fix the Rheem Water heater’s red light flashing 7 times.

1. Rheem Water Heater Chamber Sensor Failure

In many cases, if the thermocouple or the flame sensor fails, the pilot light will not be lit, which affects the complete ignition system. This triggers the 9-blinking error. 

Most often, a bad chamber sensor lets the gas valve remain open and supplies gas even after the water temperature has already reached the set temperature. 

This overheats the heater and catches the 9-time blinking error. Below, you will find all the possible reasons for chamber sensor failure and how to resolve it.  

i). Clogged Flame Sensor

In many cases, it seems that the flame sensor gets clogged by shoots building up on the sensor body. If the dirt and debris are stuck on the sensor, the sensor won’t continue its function. 

When the flame sensor fails, the pilot might be unable to ignite, or the burner won’t stay lit. That may lead to sensor failure. So, cleaning the element can fix the issue for the most part. 

How To Clean Flame Sensor On Rheem Water Heater

  • Before starting the cleaning, turn off the power to the heater. 
  • Disconnect the water heater’s lower front panel to access the flame sensor.
  • Pull out the burner assembly very carefully to clean the flame sensor.
  • You may remove the sensor from the assembly for better cleaning. 
  • Now, you will find stuck debris on the sensor body.
  • Take 400-grit sandpaper and start wiping the surface of the sensor.
  • Once cleaning is done, reassemble the flame sensor and burner assembly back into place. 
  • Connect the power connection and turn the unit on. 

ii). Test The Chamber Sensor

An incorrect voltage reading of the chamber sensor is one of the big culprits behind its failure. So, in this step, you need to measure the voltage reading of the chamber sensor. 

It will define if it is still working or not. Also, we can’t assure that the sensor is defective until we measure its resistance. However, test whether the chamber sensor is working by following the below methods:

How To Test Chamber Sensor On Rheem Water Heater

  • In order to test the chamber sensor, first, you need to get access to the sensor. 
  • Locate the sensor from inside the combustion chamber.
  • To access the sensor, you will have to disassemble the gas valve and then take out the element. 
  • Don’t detach the sensor from the water heater’s backplate.
  • Take a multimeter to measure the voltage. Set the reading to ohms.
  • Get pin probes and attach them to the multimeter. 
  • This will let you test the pins on the small plastic connectors without any damage.
  • Now, insert the pin probes into the center and outside holes. 
  • Take resistance reading. Also, measure the water temperature.
  • Now you need the heater manufacturer’s chart to compare the resistance at different temperatures.
  • If you find the resistance is all ok, then be sure the chamber sensor is quite fine.
  • Here you need to replace the defective gas control valve.
  • On the contrary, if the reading is out of range, replace the chamber sensor. 

Replace The Defective Chamber Sensor

If the chamber sensor fails, you need to replace and install the new sensor to get the heater back to operate again. There are some quick signs to define that the chamber sensor is defective. That includes:

  • Broken or bent sensor.
  • Loose connection of the sensor in the combustion chamber
  • Worn-out sensor.
  • Wrong voltage reading

However, in this stage, you will find a description of how you will replace the defective sensor effectively.

How To Replace Chamber Sensor On Rheem Water Heater

To replace the faulty chamber sensor, you will need a Rheem chamber sensor replacement kit.

 replace the chamber sensor

In the kit, you will find all the tools that you need while replace the chamber sensor. Or, collect the below listed required tools:

  • 11/32 nut driver/socket
  • T20 Torx 
  • ¾ inch wrench 
  • ½ inch wrench
  • 7/16 inch wrench
  • 3/8 inch wrench

Now, follow each of the steps described below to replace the bad chamber sensor:

  • Before starting to replace it, unplug the power connection of the heater.
  • Shut off the gas shut-off valve.
  • Next, remove the burner access cover. Take T20 Torx to unscrew the screws attached to the cover. Also, disconnect the attached nut using a nut driver.
  • Disconnect the thermopile and the igniter from the gas valve.
  • Use a ¾ inch wrench and disconnect the main gas supply from the valve.
  • You have to disconnect the pilot gas supply using a 7/16-inch wrench.
  • Remove the screws of the burner assembly and pull it out carefully.
  • Then, loosen the sensor using a ¾ inch and ½-inch wrench.
  • Remove the faulty sensor by unscrewing it.
  • Now place the new sensor there. 
  • Connect the sensor head in the front place and then attach the hex rod to it.
  • Ensure a tight connection of the chamber sensor.
  • Slide the burner assembly back into the combustion chamber and reassemble the heater.
  • If the task seems hard to you, you may contact a certified plumber to do this precisely.

2. Flammable Vapor Sensor Problem

Rheem water heater red light flashing is not only related to the chamber sensor but also there may be a problem with the flammable vapor sensor.

FVS is a safety device for the heater, which causes a soft lockout when the device finds any flammable vapor nearby the unit. 

In this mode, the gas valve stops functioning, and the pilot light shuts down to prevent the possibility of the vapor’s unsafe ignition. 

Now let’s know the reasons for FVS soft lockout mode:

What Causes Flammable Vapor Sensor Lockout

The flammable vapor sensor works by changing its resistance. When the sensor senses the presence of flammable vapor, which can be ignited by the burner, the resistance of the sensor increases. 

Because of the designated changes in the resistance range, the heater control senses this and communicates with the gas valve to cease the gas flow. As a result, the heater won’t heat the water and flashes 9 times, blinking on the red light.

There are some of the most common things that can trigger the FVS and lead to soft lockout mode. For instance:

  • Ammonia or sewer gas
  • Butane
  • Gasoline
  • Isoprene
  • Kerosene
  • Bleach
  • Paint
  • Benzene
  • Mineral Spirits
  • Or harmless events like pet accidents

Rheem Flammable Vapor Sensor Lockout Reset

When the heater is in a soft lockout mode, the only way to get rid of this mode is to reset the FVS. Or, you need to replace it if the sensor resistance is out of range or defective.

How To Reset Flammable Vapor Sensor On Rheem Water Heater

Follow the below instruction on how you reset the FVS lockout to turn back on the heater:

  • First, disconnect the power connection from your water heater.
  • Wait for about 10-20 seconds.
  • Then plug the heater back into the power connection.
  • Wait for the next 5 seconds.
  • After that, press both arrows together on the valve and hold them for 5 seconds.
  • When the green LED blinks, you will have to enter a code by pressing the arrows.
  • That code is “Left, Right, Left, Left, Right, Left, Right, Right.”
  • The heater will be reset, and all the LEDs will light. That signifies that the error has been cleared out.

Flammable Vapor Sensor Resistance Out Of Range

Most often, the FVS fails to start operating again even after resetting the lockout. A faulty resistance setting on the sensor can also be the culprit.

A healthy FVS should give a resistance reading between 11k ohms-45k ohms. Now, check the resistance of the sensor.

How To Test Rheem Flammable Vapor Sensor

First, disconnect the sensor from its bracket on the base ring of the water heater. Disconnect the sensor wiring. Take a multimeter and connect the lead between the two terminals on the sensor.

test the  rheem flammable vapor sensor

Start taking the resistance reading between the two wiring terminals of FVS. If the reading is under 11k ohms or above 45k ohms, be sure the FV sensor is defective. Replace the faulty FVS.

3. Rheem Water Heater Gas Control Or Valve Failure

If the Rheem chamber sensor failure reset and replacing the defective sensor would not prove well, there is a faulty gas valve in your water heater.

Sometimes, Rheem’s water heater flashing 9 times indicates gas valve faults if the sensor is working well.

 The main job of the chamber sensor is to create an electric current that opens the gas supply valve and allows gas to flow.

Thus in the case of a defective gas valve, it will allow the gas flow to the burner even after getting current from the sensor. So, In such a case, as the problem would be with the gas valve, we need to replace the faulty element.

How To Replace Faulty Gas Control Valve In Water Heater

Here are the steps for the Rheem water heater gas control valve replacement:

replace the faulty gas control valve
  • Turn off the heater and shut off the gas supply valve.
  • Disconnect the lines connected to the gas control valve 
  • Remove the burner assembly from the water heater.
  • Now disconnect the old gas valve using a wrench.
  • Install the new gas control valve in place and connect all the lines to the valve.
  • Connect the gas line with the valve. 
  • Reassemble the burner assembly and turn on the heater.
  • Turn on the gas supply and light the pilot. 
  • Hopefully, the Rheem water heater blinking red 9 times has been resolved.


What is the life expectancy of a Rheem water heater?

The life expectancy of the water heater depends on how you are operating this unit. But from the manufacturer’s recommendation, the typical lifespan of the Rheem water heater is in between 5 and 15 years.  

What is the most common problem with the Rheem water heater?

The most common problems with the water include water leaking, the pilot not lighting or not staying light, improper water pressure, heater overheating, or water taking too long to heat.

Wrapping Words:

Hopefully, we’ve assisted you in finding every responsive factor for chamber sensor failure on the Rheem water heater. Also, we have explored all the well-proven solutions for each aspect.

Now you will not face any trouble while resolving this blinking error from your heater. Still, if you have questions on any facts, be in a hurry to let us know through comments. We will be happy to help you with the best solutions.

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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