Why Rheem Water Heater 6 3 Flashes [Reason + Solutions]

Your Rheem water heater 6 3 flashes mean the recycle limit-flame loss. The major causes of this error are gas valve malfunction, ventilation problems, and defective flame sensor.

However, the other culprits to be blamed for this hitch are:

  • Leaky bottom valve 
  • Inadequate combustion air 
  • Malfunctioning pilot tube 
  • Cracked insulation
 rheem water heater

Quick Solution: 

For whatever causes the error code occurs, first, we recommend you reset your heater. If the reset doesn’t work, the problem is somewhere else in your heater. 

However, before you get crazy about fixing the above troubles, go through this guide. And you will surely learn the resolving ways. 

Rheem Water Heater 6 3 Flashes [Reason + Solutions]

The major causes of 6 3 error code on your Rheem water heater, and their effective fixing ways are:

Note: You can also read how to fix Rheem tankless water heater code 11.

1. Defective Gas Valve

The gas valve malfunction causes flame loss in your Rheem water heater. The faulty valve interrupts the gas supply to the burner and pilot light. Ultimately it results in 6 3 times blinking in your heater. And then the unit shuts off by itself.  

rheem water heater defective gas valve

However, the potential culprits of malfunctioning valves are the damaged or dirty gas valve and safety circuit glitch. Also, the bad electronic gas ignition components can cause it. 


The gas valve allows the gas to flow from the gas supply line of your heater to the main unit. However, due to the lousy gas valve, your heater fails to create a stable flame and stops producing heat.

Therefore to fix the 6 pauses 3 error code on your heater, start by checking its gas valve. If there is any dirt on the valve, clean it. In case the valve becomes damaged, you must replace it. 

Also, inspect the electronic ignition components within your Rheem heater. When you find any part is defective, you must replace that one. And finally, remove the glitch from the safety circuit in your heater. 

2. Malfunctioning Flame Sensor

The 6 3 flashes error code on your Rheem water heater means the recycle limit-flame loss. As an immediate repercussion of flame loss, your heater will turn off.  

rheem water heater flame sensor

However, the lousy flame sensor causes flame loss in your heater. The potential reasons for this trouble are the defective or dirty sensor and cracked insulator. 


Begin by cleaning the dirt from the sensor. During the sensor cleaning, you must replace it if you find it is damaged. Also, inspect the insulator and replace the cracked one. 

How To Clean & Replace Your Rheem Water Heater Flame Sensor

Now we will walk you through the easy steps of cleaning and replacing the flame sensor. And those are:  

pull out the rheem water heater sensor

Step 1: Firstly, turn off your Rheem water heater. In case you don’t find the switch, shut off the main circuit breaker in the electrical panel. Then remove the front cover of your heater to access the panel. And you will get the flame sensor right in front. 

Step 2: Now, you will find that the white (sometimes turned brown or yellow) porcelain base sensor is attached with a single wire. You must pull the wire from its terminal and disconnect it. Anyway, pull hard so that the spade connector doesn’t get stuck. 

Step 3: In this step, loosen the screw holding the sensor using the flat-head screwdriver. After that, pull out the sensor and keep the screws safe.

Step 4 (Clean The Sensor): Now it’s time to clean the sensor probe. Rub the sensor with fine steel wool, sandpaper, or emery cloth and remove its carbon deposits. Clean properly and make sure the probe has a shiny silver hue. One recommendation is to avoid rubbing the probe hard, as it is fragile.

Step 5 (Replace The Flame Sensor): In case, after cleaning the sensor, it won’t work and you need to replace it, then this step is necessary. To replace the old one, take a new flame sensor first. Then insert the new probe into the burner housing hole properly. 

Afterward, secure the sensor by tightening the screws. Now back onto the terminal, push the connector of the sensor wire. And the replacement process is done. 

3. Ventilation Issue

Due to insufficient ventilation, your Rheem water heater can blink 6 3 times over and over. Ultimately due to this recycle limit-flame loss error code, the pilot won’t light, and the unit will lose heat. 

However, the ventilation problem includes the following:

  • Blocked exhaust vent
  • Inappropriate vent size and length


The simple way to fix the ventilation of your heater is to remove the blockage from the exhaust vent. Also, make sure the vent size and length are appropriate. 

4. Leaky Bottom Valve

You can get the 6 flash on your heater, followed by the 3 flash error code due to the leaky bottom valve. When your water heater leaks from the bottom, you can experience this error code.


First, put your finger in the bottom of your Rheem water heater. Then check for water in it. If the water leak is the culprit, you will find water in the bottom. In case of a leaky heater, you must fix the leak immediately. After covering up the leak, wait to dry it up. 

The leak can be dried quickly or can take a few days. We suggest you put a fan in front of the repaired leak. And it will dry up quickly. 

5. Insufficient Combustion Air

Inadequate combustion air causes the improper operation of your Rheem water heater. And thus, your heater loses flame. Moreover, the main burner and pilot light fail to function correctly due to the combustion air blockage. And thus, your heater fails to heat water to the set point.

However, your Rheem water heater stops working and loses efficiency due to poor combustion. Ultimately the unit shows the 6-3 error code. Anyway, combustion air insufficiency happens due to the following reasons.

  • Insufficient fresh air supply or inadequate ventilation
  • Dirty air filter or air inlet holes


When your heater loses flame, we suggest you inspect the air inlet hole and filter. Verify these and ensure sufficient fresh air circulation. 

Make sure your heater for the combustion process is getting adequate air and nothing is blocking the air supply.

6. Pilot Tube Problem

Any issue with the pilot tube causes an inadequate fuel supply. As a result, your heater doesn’t get enough fuel to produce an intense flame. 

rheem water heater pilot tube problem

Due to insufficient fuel, your Rheem heater loses flame and flashes 6 3 times. However, the reasons for the pilot tube malfunction in your Rheem heater are:

  • Dirt or any other objects build up in the pilot tube.
  • A broken or loose gas valve creates pressure in the pilot tube.
  • Misaligned tube


The ways to settle down the above troubles are simple. Firstly, you must check the pilot tube. And verify whether your heater is getting fuel supply or not. If not, then fix the above hitches following the ways below:

  • Remove the dirt or debris from the pilot tube. And it’s better to follow a cleaning routine regularly, so grime can’t accumulate on the tube.
  • Then check the gas valve. Replace the broken gas valve, and tighten the loose one. And make sure the gas pressure is sufficient.
  • Lastly, replace the broken or bent tube. And properly place the misaligned tube.

7. Cracked Insulation

There is insulation in the back of the pilot light assembly in your Rheem water heater. The cracked small insulation strip can also cause the 6 3 blinking error code on your heater. The damaged insulation fails to prevent heat loss. And thus, this error appears.


We recommend you to buy some pipe insulation and cut a 12 inches long strip. Also, cut the insulation pipe width-wise in half. Secondly, make sure the strip surrounding your water heater bottom covers the holes completely.

Otherwise, set it into your heater inside part with the foil. Finally, put the screws back in place and tighten the screws to fix this hitch.

How To Reset The Rheem Water Heater

Resetting restores the previous functioning of your Rheem water heater. And it fixes the error code blinking hitch also. However, to reset your Rheem water heater follow the step-by-step instructions below: 

  • A reset button is available in your Rheem water heater. Usually, this red reset button is located in the middle of the limit switch. Or sometimes, it can be located near the thermostat. So, first, you must find it. 
  • Once you find the button, we suggest pressing and holding the red reset button as long as you don’t hear the clicking sound. 
  • After hearing the clicking sound, leave the reset button, and the reset is done.


Why does my pilot light keep going out on my Rheem water heater?

The pilot light keeps going out mainly due to the faulty thermocouple, inadequate gas supply, dirty pilot light, etc.

What does the red flashing light on The Rheem water heater mean?

The red flashing light means your Rheem water heater needs to reset as it enters into the lockout condition. Stop using your heater until you fix the red light blinking issue on your heater. 

How do you check the pilot light on a Rheem water heater?

Through the viewing window of the inner door of your heater, inspect the pilot light. Hold the red button after the pilot lighting continuously for one minute, then leave it.

Final Words

So now you know all the major reasons for which your Rheem water heater 6 3 flashes. Fortunately, you don’t need to think much about these hitches as we have explained the resolving ways also. 

Follow our suggested ways above, find the culprit, and fix this issue yourself at home. 

However, don’t feel shy to comment if you fail to solve the flashing code on your heater. We are always here to help you.

About David

David is a man who loves doing research and finding out the best solution to any type of heating appliance issues like heaters and fireplaces. Whenever he finds the perfect solutions to any issues of heating appliances after doing in-depth research, he loves to share them with his readers. In fact, his aim is to help his readers to fix the issues with their heating appliances easily.More about us .

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