Rheem Water Heater 8 Flashes Then 1 [Reasons + Solutions]

Rheem water heater 8 flashes then 1 in blue light is the error indication of the FVS fault detection due to wiring or electronic issue. When the flammable vapor sensor is out of range, or faulty sensor wirings are the leading reason behind the FV sensor failure. Also, a faulty gas control valve may be the culprit.

rheem water heater 8 flashes then 1

While troubleshooting this error, you need to test the FV sensor and replace it if needed. If the error will still blink, replace the defective gas control valve. Read through the below comprehensive article to get a well-proven guide in fixing the blue light  8 flashes of the water heater.  

Why Rheem Water Heater 8 Flashes Then 1 [Solved]

Let’s have a glimpse at the FV sensor and what causes FVS faults on the Rheem water heater. 

What Is a Flammable Vapor Sensor In Water Heater

A flammable Vapor or FV sensor is a safety device for water heaters. It is the responsive element for causing soft lockout and turning off the heating system after finding any flammable vapor nearby the unit. FV sensor functions by changing its resistance. The sensor’s resistance will increase when it senses the presence of flammable vapor that may ignite. 

Due to designated changes in the resistance range, the heater detects it as an error and flashes blue light 8 then 1. Besides, the wiring of the FV may worn out after long wearing and tearing.

Also, the vapor sensor may be burnt out. From below, learn all the responsive factors behind the water heater blue light flashing 8 times then 1 and how to fix the error.

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

1. Rheem Water Heater Flammable Vapor Sensor Reset

If the Rheem water heater goes out of specification mode and blinks blue light 8 times, the only way to erase the error is to reset the FVS. Follow the below instruction to reset the flammable vapor sensor of your water heater.

How To Reset A Rheem Flammable Vapor Sensor

  • First up, remove the power connection from your Rheem water heater.
  • Leave the heater unplugged for about 10-20 seconds.
  • Then connect the power connection back to the heater again.
  • Wait for more than 5 seconds.
  • You will see two arrows on the control valve of the water heater. Just press both arrows simultaneously on the valve and hold them for 5 seconds.
  • Wait until the green LED blinks. Once it blinks, enter a code by pressing the arrows.
  • The code will be “Left, Right, Left, Left, Right, Left, Right, Right.”
  • That’s it!! Your heater is reset, and all the LEDs will light. That signifies that the error has been cleared out.

2. Flammable Vapor Sensor Resistance Is Out Of Range

If your Rheem water still flashes 8 times even after resetting the FVS sensor, be sure the faulty resistance setting on the sensor is now the culprit. When the FV sensor resistance is out of range, the heater detects it as a fault and goes out of the specification mode.

A healthy FVS resistance range should be between 11k ohms-45k ohms. Now check and verify if your water heater gives a resistance reading in this range or not.

How To Test Rheem Flammable Vapor Sensor

Here are the steps to measure the resistance of the FVS on a water heater. 

test rheem flammable vapor sensor
  • First of all, remove the FV sensor from its bracket. You will find the bracket on the base ring of the water heater. 
  • Then, disconnect the sensor wiring harness.
  • Now you will need a multimeter to test the FVS.
  • Connect the lead between the two terminals on the flammable vapor sensor.
  • Now see the resistance reading between the two wiring terminals of the FV sensor. 
  • If you find the reading is under 11k ohms or above 45k ohms, be sure the FV sensor is faulty. Replace the defective FVS to get the heater back in operation again.

3. Replace The Defective Flammable Vapor Sensor

If the FV sensor is not providing the correct resistance reading, you need to replace the defective FV in this step. 

replace rheem bad flammable vapor sensor

We have included all the  DIY methods to replace the defective FV sensor from your Rheme m water heater.  

How To Replace Rheem Bad Flammable Vapor Sensor

Go through the below instructions for Rheem flammable vapor sensor replacement.

  • First, locate the FV sensor from the front center of the water heater just below the outer door.
  • Remove the outer cover door from its place.
  • Now pull the sensor wiring from two terminals of the sensor cap and disconnect the old FV sensor.
  • Before installing the new FV sensor, ensure the installation environment is free from flammable or other potential sensor-contaminating vapors. 
  • Connect the new sensor to the wiring connections.
  • Then, push the sensor wiring into the sensor cap until it snaps into place.
  • Reassemble the front cover of the water heater. 

Rheem Water Heater Flashing Red Light 8 Times [False Pilot Flame Signal]

If your Rheem water heater red light blinks 8 times in a 3-second pause, it is the error indication of a false pilot light signal in the ignition system. Here, the pilot valve is stuck in an open position, which is why this error blinking.

A stuck pilot valve problem occurs when you have shut down the heater, but the heating element has failed to turn off. 

A defective gas control valve is the root culprit for this issue. The pilot control knob may be stuck in one position and creates problems in turning off the heater. Here are the suggested methods to troubleshoot this error.

i). Reset The Gas Control Valve

First, turn up the gas control knob to the “Off” position. Wait for about 5-10 seconds. Then set it to the “ON” position. If one attempt fails to resolve the issue, repeat the steps 2-3 times. 

This will reset the gas control valve of the water. Also, it will help to fix the stuck pilot knob problem and erase the error. 

ii). Replace The Faulty Gas Control Valve

If the water heater red light blinks 8 times even after resetting the gas valve, be sure the gas control valve is defective.

You need to replace the faulty gas control valve. It is highly recommended to contact a professional to do this task for you.

iii). Relight The Pilot Light

After replacing the gas control valve, your next step will be to relight the pilot light. Follow the below instructions to relight your water heater pilot light.

How To Relight A Rheem Water Heater Pilot Light

  • First, rotate the gas knob clockwise until the knob is set in the “Off” position.
  • Now, set the water-heater temperature dial to the lowest setting.
  • Wait for five minutes. Meanwhile, the inside gas of the water will pass through.
  • Then, rotate the gas knob to the “Pilot” position.
  • Press the red button on the gas knob.
  • Keep holding the piezo igniter striker at the same time.
  • You will see that the pilot is started lighting. Continue to hold down the button for one minute after the pilot is lit. Then, release the button.
  • Reconnect the water heater’s outer door.
  • Rotate the gas knob to “On” and set the temperature as per your preference.


Why is my hot water heater continuously running?

Leakage inside the water heater is the leading reason for continually running the heater. Also, malfunctioning in the temperature setting causes the issue. Due to insufficient insulation in the water heater, the temperature will start fluctuating. 

How do I know if my water heater element is burnt out?

Sometimes, it seems that the water is not getting hot or the water temperature is not reaching the set one, be sure any of the heating elements has burnt out. Also, the incorrect resistance reading of the heating element is a big sign of its faults. 

How often does a hot water heater need to be replaced?

A hot water heater lasts up to 8-10 years if you ensure the correct maintenance of it. But as the manufacturer recommends, you should replace your water heater after 10 years because of safety. 

Wrapping Words:

To the ending point of this guide, hopefully, now you know the reasons for occurring 8 times flashing on the Rheem water heater. Also, you have learned the corrective actions to fix the issue effectively. 

Just follow the suggested methods and erase the error from the LED light. Still, if you have any queries or questions regarding any above facts, let us know through a comment. We are here for you at all times!!

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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