Why Is My Rheem Water Heater Blinking Red Light?

Rheem water heater is blinking red light due to an extinguished pilot light, low thermopile voltage, a tripped reset button, and a faulty gas control valve. Even the water heater status light will blink under normal operation. 

How often the status light blinks the read will help determine whether the flashing red light is a problem or normal. Fortunately, we break down everything you need to know about the blinking red light. So, stay in tune with us till the end. 

Table of Contents

What Does A Flashing Red Light Mean On Rheem Water Heater?

A flashing red light on a Rheem water heater means either the unit is operating well or something is going wrong. How many times the water heater blinks the red light will determine whether the heater is running at its tip-top condition or not. 

For example, the water heater will flash a red light only one time every three seconds at normal operation. But, two red light flashes every three seconds means there is low thermopile voltage and you need to address & solve this issue. 

In short, the blinking red light on a water heater will help diagnose an issue the unit is going through. 

Read Also: Rheem Tankless Water Heater Troubleshooting Manual

Why Is My Rheem Water Heater Blinking Red Light?

Your Rheem water heater is blinking red light for the following reasons: 

01. Pilot Light Gets Extinguished

If your Rheem water heater blinks red light constantly, we bet the Pilot gets extinguished. Therefore, the heater will continuously light because the thermopile is getting cold down or you set the temperature knob to Off position. 

How To Fix: 

To solve this issue, you need to relight the pilot of your water heater. Follow the below instructions to learn how to relight the pilot light on the Rheem Water heater: 

  • Set the combination gas control or thermostat knob to the Off position by rotating the knob counter-clockwise. 
  • Leave the water heater for five minutes to clear out any gas. Make sure you smell no gas. If you do, don’t try to light any appliance, even don’t touch any electric switch. Call a gas supplier using your neighbor’s phone. 
  • Pull out the outer door from the water heater. Then, locate the piezo-electric spark generator button, which you can find below the thermostat knob. 
  • Now, set the thermostat knob to the Pilot position by rotating it clockwise. 
  • Hold down the thermostat knob all the way in. At the same time, keep depressing the piezo-electric spark generator button several times until the Status indicator light starts blinking. Once the Status light comes or begins blinking, ensure the pilot is lit by seeing the pilot flame through the sight window. If the pilot light doesn’t come on at the first attempt, repeat the steps from 1 to 5 again. 
  • Bring the outer door back into its place. 
  • Release the thermostat knob. 
  • Now, set the thermostat knob to your desired temperature setting. 

02. Normal Operation

During normal operation, your Rheem water heater just blinks the red light 1 time every 3 seconds. In other words, you don’t need to worry about it as the temperature knob is in the pilot position and the pilot is lit.

How To Fix:

You don’t need to do anything in this case. What you should do is- just set the temperature control knob to your desired temperature setting and walk away. 

03. Low Thermopile Voltage

Your Rheem water heater will blink red light two times every three seconds if the thermopile voltage is low. It is a must to have proper voltage on the thermopiles to get hot water from your water heater. 

If the thermopile voltage is low, the pilot light will go out. Consequently, you can’t enjoy the steamy water you get every day for a comfortable shower. 

Several reasons are responsible for a low thermopile voltage. For example, high winds can blow out the pilot, which stops the voltage of the thermopile. Open windows and doors can also cause the draft even though you keep the water heater inside your home. 

Besides, loose thermocouple connectors between the thermopile and the combination gas control can also cause low thermopile voltage. Damaged thermopile wires are also responsible for low voltage on thermopiles. 

How To Fix:

We recommend you test the thermopile to see whether it is bad or not. Fortunately, you don’t need to be a tech nerd to inspect the thermopile for low voltage. Follow the below steps to check the thermopile: 

  • Take a multimeter for direct current and set it to millivolts.
  • Wiggle the thermopile connector a little bit and pull it out from the gas control. 
  • Attach the red positive lead to the red thermocouple wire and the black lead to the other (white) wire. 
  • Now, light your pilot light according to the manual. Fortunately, we mentioned above how you can light the pilot light on the Rheem water heater. 
  • Depress and hold the thermostat knob down until it reaches the maximum voltage. It may need three minutes to reach the highest voltage. After that, the reading on your multimeter will start slowing down. 
  • A healthy thermopile voltage reading should be 650 to 850 millivolts. If the test gives the reading below 400 millivolts, you should replace the thermopile. 

You can check out the following tutorial to replace the thermocouple. 

Also, make sure the thermopile connector to the combination gas control is okay. Ensure the thermopile wire is intact. Of course, don’t forget to inspect the pilot assembly as well. 

04. Reset Button Gets Tripped

Your Rheem water heater also blinks the red light when the high water temperature limit switch or reset button gets tripped. In this, your water heater will flash the red light 4 times every three seconds. 

The water heater keeps tripping the reset button due to the following reasons: 

  • A bad heating element
  • A defective thermostat
  • Loose wiring connection
  • A faulty reset button 

How To Fix: 

Start with inspecting the heating element. We recommend you shut the power off and detach the wiring to the heating element and use an ohm meter to measure the resistance. The reading should be 18 ohms. If the reading is significantly different from the readout, you should replace the heating element. The following tutorial from Rheem will help you regarding the heating element replacement. 

Don’t forget to check the wiring for loose connections. If you have no ABC knowledge of electricity, we recommend you hire a certified plumber to do this task for you. Also, check the reset button. If it doesn’t work anymore, you need to replace the whole thermostat as the reset switch is part of it. 

05. Gas Control Valve Gets Defective

A faulty gas control valve is another culprit that also causes the status light to blink red flash. Typically, your water heater will flash red light 7 times every three seconds if the combustion gas control valve is at fault. 

If the gas control valve gets defective, the heater unit will not flow sufficient fuel to ignite the water heater. Consequently, you will get no hot water from the unit. Several reasons are responsible for the faulty gas control valve. They are: 

  • Worn out thermocouple
  • Electric gas ignition elements get faulty
  • The control valve itself gets defective

How To Fix:

Most often it’s the valve itself that is at fault. In this case, you must replace the gas control valve. If you are mechanically inclined, you can find the following tutorial helpful: 

Alternatively, it would be best to hire a certified professional to do this task for you. 

Read Also: Rheem Tankless Water Heater Error Codes

How Do I Reset My Rheem Water Heater?

The following steps will help you reset your Rheem water heater: 

  • Turn the power switch off and flip the heater’s switch at the circuit board to switch off the water heater. 
  • Access the limit control switch by removing the front panel. You can find this button near the thermostat. 
  • Press the reset button, which is in the middle of the limit control switch. 
  • Finally, put the front panel back into its place and turn on the power switch and flip the heater’s switch at the circuit board. It will reset your water heater and you can see no error codes on the display. 


Should water heater light be blinking?

Yes, the water heater light should be blinking. Flashing the status light of your heater doesn’t always mean it’s dangerous. Rather, it will notify you when the water heater needs your attention. Above all, most water heaters now shut themselves off before anything becomes hazardous.

Why is my Rheem water heater not turning on?

Your Rheem water heater won’t turn on due to a tripped circuit breaker, a tripped limit switch, or faulty heating elements. If the heater gets no power, you can’t turn the heater on.

Why does my Rheem water heater keep shutting off?

Several reasons are responsible for the Rheem water heater to keep shutting off. Some of them are dirty thermocouples, damaged thermocouples, a defective gas control valve, and a dirty pilot tube. Once you address and solve these issues, you can run the water heater smoothly.

Why does my water heater not stay lit?

A bad or dirty thermocouple is the main culprit behind this issue. If it gets covered with dirt or damaged over time, it can’t sense the pilot light and stop the gas flow. Consequently, your water heater won’t stay lit.


Blinking red light on Rheem water heater means your heater will go into the lockout mode and it needs your attention. Now, what you need to notice is how often it flashes the red light. 

If it flashes the red light just 1 time every three seconds, there is nothing to worry about as it indicates normal operation. But if the status light blinks two, four, or seven times every three seconds, understand there is something going wrong with your water heater. 

In short, flashing red lights will help you determine whether the water heater operates smoothly or not and when it requires your attention. 

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