The flashing code ‘8-1 FVS’ on the water heater indicates the FVS fault is detected and your Rheem Water Heater enters Hardware Error Lockout.
If you want to bring your water heater back to normal operating condition, you should find the source of this issue and solve it. And this troubleshooting guide will help you to do that.
So, let’s get started right here.
Table of Contents
- What Does The Flashing Code ‘8-1 FVS’ Mean On Rheem Water Heater?
- Rheem Water Heater 8 Flashes Then 1: The Why & How-To Fix
- How Do You Reset the FVS On A Rheem Water Heater?
- End-Notes
What Does The Flashing Code ‘8-1 FVS’ Mean On Rheem Water Heater?
Flashing code ‘8-1 FVS’ on Rheem Water Heater stands for FVS fault detected. Your water heater will throw this error code between three-second pauses because of wiring or electronics issues, especially bad FVS wiring.
The control will turn off every output (valves closed, inducer off, ignition off) right off the bat once the water heater flashes this error message. Your water heater even goes into the Hardware Error Lockout and registers a Flammable Vapor Device Interface/Miswiring error code.
Rheem Water Heater 8 Flashes Then 1: The Why & How-To Fix
Rheem Water heater 8 flashes then 1 or flashing ‘8-1 FVS’ means the FVS or Flammable Vapor Sensor gets faulty. FVS sensor resistance goes out of range, wiring to FVS is at fault, or defective gas control are the culprits behind this issue.
| Error Code | Meaning | Reasons |
| 8-1 Flashes | FVS (Flammable Vapor Sensor) Fault Detected | Flammable vapor sensor resistance goes out of range |
| Wiring to FV Sensor is at fault | ||
| Faulty Gas Control |
You can easily clear the flashing code ‘8-1 FVS’ by addressing & solving those caveats I mentioned. And luckily I am here to help you out in this case. Below, I will break down everything to fix the issue.
01. Flammable Vapor Sensor Resistance Goes Out of Range
The resistance of a healthy or functional Flammable Vapor Sensor should be between 9k Ohms and 45k Ohms. If the resistance climbs above or down this range, understand there is a problem with the FVS.
Without testing, you can’t accurately say the FVS resistance goes out of range. In the ‘How To Fix’ section, I will show you how to test the FVS for resistance.
How To Fix:
Begin the inspecting workflow by testing the flammable vapor sensor electrically. To test the sensor, you should have a multimeter.
First off, set the gas control to the Off position.
Secondly, detach the flammable vapor sensor from the gas control. You can find it at the bottom of the water heater. Of course, you need to remove the access panel to disconnect the FVS.
Now, set your multimeter to Ohm setting and attach the two leads to the two terminals of the flammable vapor sensor. If the multimeter gives a reading between 9K to 45K Ohms, the FVS is okay. Otherwise, the resistance of the sensor goes out of range.
In this case, you should replace the flammable vapor sensor. The following tutorial will help you change the FVS:
02. Wiring to FV Sensor Is Faulty
Faulty or damaged wiring leading to the flammable vapor sensor is also to blame if your water heater flashes 8-1. If this wiring gets worn out or insects like critters cut the wires, your water heater will flash the error code ‘8-1 FVS’.
How To Fix:
Make sure the wire harness is in good condition. If it gets damaged, replace it with a new one.
In this case, connect the FVS to the wiring connectors located at the front center of the water heater just below the outer door. Then, push the sensor and the wiring into the sensor cap until it snaps in place.
However, if you are not electrically inclined, hire a professional (though I believe you can do this on your own).
03. Faulty Gas Control
If the problem persists despite replacing the flammable vapor sensor and its wiring harness, I bet the gas control valve is at fault. In this case, changing the gas control valve is the only option.
How To Fix:
I highly recommend you hire a professional plumber to replace the Honeywell gas control valve. However, if you want to DIY this, you can find this tutorial helpful:
How Do You Reset the FVS On A Rheem Water Heater?
Resetting the FVS or flammable vapor sensor on your Rheem Water Heater is just a piece of cake. It will help you bring the water heater out of the Hardware Error lockout.
To reset the flammable vapor sensor, what you need to do is-
Firstly, turn off your water heater and wait for 10 seconds
Secondly, plug the power back and turn on your water heater.
Now, you have only 3o seconds to switch the temperature dial. Just rotate the temperature dial all the way from the vacation setting to all the way to the very hot settings.
In short, you should back and forth the dial from the vacation or pilot setting to the very hot settings 7 times within 30 seconds. And it will reset the flammable vapor sensor successfully.
Read Also:
- Rheem Water Heater Troubleshooting Manual
- Rheem Water Heater Error Codes
- Rheem Water Heater Blinking Red Light
End-Notes
Replace the flammable vapor sensor and its wiring harness if your water heater flashes ‘8-1 FVS’ on display. If still, your water heater throws this error code, I bet the gas valve control is at fault. So, replacing this part will bring luck to you.
Don’t hesitate to call the technical support if needed to verify it’s the FVS vs. the Gas Valve. However, they will ship you both parts for free if your water heater is under warranty.
Good Luck!
Eric Alvarez is the head of content on LilDutchUncle.Com. He is an HVAC guy based in El Paso, Texas, United States. He obtained his Bachelor of Science degree from the University Of Texas at El Paso. Years of experience in the HVAC field have taught him many lessons, not the least of which is that the value of quality and knowledge far exceeds any promised initial savings. He has a good standing reputation for superior skills in heating, air conditioning, hot water tanks, and indoor air quality systems.
