Rheem Water Heater Red Light Flashing [7 Blinks Solved] 

Rheem water heater red light flashing at a different number of times indicates several malfunctions from the heater element. If the heater’s red light blinks for 1 time, that is a sign of the normal operation, and there is nothing significant to do. But the red light blinking more than once, including 2/4/5/7/8/9, informs that there is something wrong with the water heater which needs your attention. 

rheem water heater red light flashing

The major errors defined by red light blinks include low thermopile voltage, high-temperature shutdown, temperature sensor failure, gas control valve failure, false pilot light signal, and chamber sensor failure.

Follow the below article to get a complete guide to fixing each error effectively.

Before moving to the detailing parts, let’s learn about why is your Rheem water heater blinking red light and what the actual meaning of it. 

Note: You can also read how to fix Rheem water heater 8 flashes then 1.

What Does Flashing Red Light Meaning In Rheem Water Heater

Rheem water heater is in the range of the most well-known brand in the HVAC industry for producing reliable and long-lasting. But most often, users face several malfunctions during operation. Blinking red light is the most common phenomenon among them.

A flashing red light on the Rheem water heater signifies that the heater has entered a lockout condition which needs your special concentration. Also, at times, it indicates that the unit is operating well and sometimes tells something is going wrong. The heater might stop functioning until you resolve the error. 

But the exact meaning of the error is mainly determined by the number of blinks. Each blinking means different malfunctions of the heater. 

1. Rheem Water Heater Red Light Flashing 1 time [Normal Operation]

Flashing red light 1 time in the Rheem water heater signifies the normal operation of the system. That means the heater is in tip-top condition, and the complete heating system is functioning quite well. The control knob is in the pilot position, and the light stays lit.


There is nothing that needs your attention or troubleshooting. Just move to the temperature control knob and set your desired temperature.

2. Rheem Water Heater Red Light Flashing 2 times [Thermopile Voltage Low]

2 times blinking on the Rheem water heater is the error indication of the low thermopile voltage of the water heaterThermopile is an essential element of systems featuring multiple thermocouples.

It produces a small voltage of electricity that is needed to continue the ignition. The circuit board is powered by this small current and starts heating the water.

But when the thermopile voltage becomes low, the pilot light goes, and the gas valve shuts down and turns off the gas supply.

rheem water heater defective thermopile

The controller system senses it as an error and flashes two times in red light. Now let’s know the major reasons behind low thermopile voltage from below:

  • Improper thermopile connection to the combination gas control
  • Damaged thermopile wiring
  • Defective connectors
  • Faulty thermopile


  • First, check the thermopile connection to see if it is properly connected to the gas control valve.
  • Also, check the connectors for physical damage. It should not be loosened and fully seated. Replace the defective connector.
  • Look for any signs of wear or corrosion in the wiring. Replace the damaged wires.
  • Now test the thermopile using a multimeter. For this, disconnect the thermopile by wriggling it a bit.
  • A good thermopile will show a voltage reading between 650 to 850 millivolts.
  • If you find the reading below 400, be sure the element is defective.
  • Replace the defective thermopile, and then the 2 blinkings will erase from the heater. 

3. Rheem Water Heater Red Light Flashing 4 times [High-Temperature Shutdown]

Rheem water heater 4 flashes signify high temperature shut down on the water heater. This error tells you that the water temperature exceeds 180 degrees Fahrenheit and the heater is shutting down. 

rheem water heater faulty thermostat

Here, the high limit switch gets tripped due to increasing water temperature to an unsafe level and turns the heater into high-temperature mode. The major reasons for causing the Rheem water heater to red light flashes about 4 times include:

  • A faulty thermostat
  • Damaged electrical wiring
  • A bad heating element
  • Gas control valve malfunctions
  • The clogged pressure relief valve
  • Defective high-limit switch


  • As a faulty thermostat is a leading reason for this, check if it gets stuck or stops working. Thermostat faults lead to the water temperature to an unsafe level. Replace the bad thermostat.
  • Then you need to reset the circuits. Just remove the two-wire connectors to the board. Wait for 10-20 seconds, and then reattach the wire connectors.
  • Now, inspect the two heating elements from the top and bottom of the tank. Test the continuity of the elements. Replace faulty heating element.
  • Check the reset button of the upper thermostat. If it is burnt out or wears out, replace the whole upper thermostat.
  • Inspect the pressure relief valve, and clean specks of dirt blocked into it.
  • Replace the bad gas control valve.
  • Check the fuel line of the valve as well. Change the fuel line if needed.
  • If still, the red light flashes 4 times, check the thermocouple now. Clean the element first. If that doesn’t work, replace the defective thermocouple.

4. Rheem Water Heater Red Light Flashing 5 times [Temperature Sensor Failure]

5 times flashing on the Rheem water heater red light tells you the temperature sensor failure. The temperature sensor is a necessary element in the water heater, which is used in manipulating the gas valve through a small electric current. It signals the gas valve whether the valve needs to release or terminate the gas supply. 

But due to this sensor failure, either the water temperature fails to reach the set temperature or sometimes rises to an unsafe level which is very dangerous. Apart from all the above, it leads to gas control valve failure as well. Accumulating sediment buildup in the sensor or damaged wiring is the root reason for temperature sensor failureHere are the steps that you have to follow to erase the error:


  • First of all, do a reset on the gas control valve. Rotate the knob to the “Off” position. 
  • Wait for about 5-10 seconds. After that time, turn the knob “ON” position. This will reset the gas valve.
  • If the error is still persisting, test the temperature sensor using a multimeter.
  • Take the resistance reading of the sensor. Measure the water temperature.
  • Now take a look manufacturer’s chart and compare the resistance at different temperatures with the readings.
  • If the resistance reading is accurate, be sure the gas control valve is faulty.
  • Replace the defective gas control valve.
  • If the reading is off, replace the dead temperature sensor.

5. Rheem Water Heater Red Light Flashing 7 times [Gas Control Or Valve Failure]

Rheem water heater’s red light blinking 7 times indicates the gas control valve failure of the heater. The gas control valve in a water heater is used to regulate the gas flow.

Due to the valve failure, it doesn’t supply enough fuel to the heater. There are some major reasons behind gas valve faults, for instance:

  • Obstructed venting
  • Clogged or damaged burner parts
  • Blocked TRD
  • A faulty thermocouple
  • A defective gas valve 
blocked thermal release device or trd

Follow the below guide to resolve the 7 blinking from the water heater:


  • First, reset the gas valve on the Rheem water heater. Turn the pilot knob to the “OFF” position.
  • Wait for about 5 minutes, and then set the control knob back to the ‘On’ position.
  • Now inspect the venting pipes and clean the stuck debris from there. Use a vacuum hose to vacuum up all the dirt.
  • Then, locate and remove the thermal release device from the housing.
  • Here look for broken or burst-out glass vial of TRD. Replace the broken vial.
  • Then, clean the scale deposits and debris from the burner assembly and its parts.
  • Unclog the combustion chamber using compressed air.
  • Also, suck up all the dirt and debris from the air intake screen with compressed air.
  • Now, move to the thermocouple and check it electrically. If the will give the voltage reading below 20 millivolts, be sure the thermocouple is at fault. Replace it.
  • If still, the red light is still blinking 7 times, a faulty gas valve is a culprit. Change the defective gas valve from your Rheem water heater.

6. Rheem Water Heater Red Light Flashing 8 times [False Pilot Flame Signal]

If your Rheem water heater’s red light is blinking 8 times, it is sure that there is a false pilot signal issue in the heating system. The error tells you that the pilot valve is stuck in an open position and interrupts turning off the heater.

A defective gas control valve is a leading culprit for this malfunction. Here the pilot knob might be stuck in one position and which is why this error is blinking.


  • In the first step, reset the gas control valve.
  • If resetting doesn’t prove well, replace the faulty gas control valve.
  • Contact any certified plumber for precisely completing the task.
  • Then, relight the pilot as instructed in the heater manuals. 

7. Rheem Water Heater Red Light Flashing 9 times [Chamber Sensor Failure]

9 time blinking on the Rheem water heater red light tells you chamber sensor failure of the heater. The chamber sensor is an important safety element that converts the heat from a burning flame into a small electrical current. 

rheem water heater chamber sensor

The current functions as a switch for opening the gas valve and starting to supply the fuel. The responsive factors for 9 times error blinking include:

  • Accumulated dirt in the sensor body
  • The wrong resistance
  • Defective chamber sensor
  • Damaged gas control valve
  • Malfunctioning of flammable vapor sensor


  • First, locate the flame sensor from the burner assembly.
  • Remove the sensor and clean the stuck debris on the sensor body. Use 400-grit sandpaper to clean the surface of the sensor.
  • After cleaning, test the chamber sensor. Take a multimeter and start measuring the voltage of the sensor.
  • Also, measure the water temperature.
  • Take the heater manufacturer’s chart and compare the resistance at different temperatures.
  • If the resistance is okay, be sure the gas control valve is faulty. Replace the bad valve.
  • But in the case of resistance changes, replace the defective chamber sensor.
  • Now move through the FVS of the heater as it may in lockout mode.
  • To fix this, first, reset the FVS sensor.
  • Then, take the resistance reading of the FVS, and it should be between 11k ohms-45k ohms.
  • If not, replace the FVS sensor.


How do you know you need a new hot water heater?

The common signs that define that you need a new water heater are getting rusty water out of the tap, making strange noises, not getting hot water, the heater overheating, water leakage, and many more.

Can a leaking water heater be fixed?

Yes, definitely!! A leaking water heater can easily be fixed. You need to fix the drain and the pressure relief valve. Also, inspect each heating element and discover the source of the leaking.


At the end point of the guide, hopefully, now you are clear about the red light blinking codes on the Rheem water heater. As each code stands for a specific problem, so you must have to know the meaning of the status codes before moving to troubleshoot. 

That is the stage our above guide will assist you a lot where you get the problem and solution with a clear description. Still, if you have any queries, feel free to ask us through comments. We will get back to you ASAP. 

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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