Rheem Water Heater Failed Ignition Lockout [Why + How To Fix]

After three successive attempts, the failure to establish burner ignition is responsible for your Rheem water heater’s failed ignition lockout. The major culprits to be blamed for this hitch are: 

  • Igniter & igniter control module malfunction 
  • Defective thermocouple 
  • Power vent & burner issue
  • Faulty gas valve 
  • Filthy spark electrode
rheem water heater

Along with the above factors, the lousy flame sensor and unplugged connectors are also responsible for ignition lockout.

Quick Solution:

First, reset your Rheem water heater to take it out of the failed ignition lockout mode. If resetting doesn’t work, we suggest you follow our guide to fix this trouble.

However, this troubleshooting guide will explain the causes and solutions of each of the above issues. So keep reading till the end.

Rheem Water Heater Failed Ignition Lockout [10 Troubleshooting Tips]

Right out after installation or using the unit for years, your Rheem water heater can show the “Failed Ignition Lockout” message. The reasons and solutions of it are:

Note: You can also read how to fix Rheem water heater 6 3 flashes.

1. Faulty Igniter

Due to the igniter malfunction, your Rheem water heater can throw the failed ignition lockout code. And after a few minutes of this response, your heater LED blinks 6 times, pauses, then again blinks 5 times, pauses, and then recycles. This ignition lockout is nothing but the 6 5 flash sequence. 

Rheem water heater faulty igniter

However, the potential causes of igniter malfunction are a dirty igniter, insufficient voltage in the igniter, and flame sensor issues.

How To Fix:

First off, visually inspect the igniter in your Rheem water heater. If you see it’s dirty, then clean it. But in case there is any damage sign on it, you must replace the igniter. 

Secondly, ensure the igniter in your water heater is getting sufficient voltage. Finally, check and fix the flame sensor hitches also. 

2. Defective Ignition Control Module

The non-functioning ignition control module fails its integrity and becomes inconsistent. Thus, your water heater goes through the ignition lockout problem. 

However, your Rheem heater ignition module becomes bad mainly for the following reasons:

  • The worn-out ignition module
  • Lousy or loose wiring connection
  • Improper alignment of the ignition control module

Along with the above causes, too-high electrical current or power surge can make the control module bad.

How To Fix:

Your Rheem water heater keeps turning off and failing to start due to the malfunctioning ignition control module. Therefore begin by checking the control module of your heater. If it is the culprit, then do the following to fix it:

  • Replace the damaged ignition module. We recommend you handle the control module correctly during the replacement, adjustment, or cleaning. 
  • Check and tighten the internal wiring connection of the control module in your heater. 
  • Make sure the ignition module is aligned correctly.

Most importantly, you must turn off your water heater during a power surge or high voltage fluctuations to keep the module effective.

3. Malfunctioning Thermocouple

The thermocouple on your Rheem water heater senses the burning pilot light. The tip of the thermocouple stays over the pilot flame. Ultimately it keeps the gas valve open by generating the voltage.

But unfortunately, the defective thermocouple fails to sense the flame. And thus, it causes an ignition lockout in your water heater. However, the potential causes of thermocouple malfunction are: 

Rheem water heater malfunctioning thermocouple
  • Dirty thermocouple or during installation and operation, it becomes damaged
  • Incorrectly positioned thermocouple
  • Using the wrong type of thermocouple

How To Fix:

Replacing the failed thermocouple is the easy way to settle the above trouble. But before directly replacing this device, we suggest you clean it. 

After cleaning the unit, when the problem still doesn’t disappear, replace it. The recommendation is to choose the correct type of thermocouple before installing it. And during the installation, correctly positioned it.

4. Power Vent Problem

After completing the maximum ignition attempts, your water heater can face failed ignition lockout due to the power vent issue. Non-functioning pressure switch on the vent can activate the ignition failure code in your heater. 

However, the power vent stops working due to the following causes: 

  • Dirty power vent
  • faulty pressure switch in the vent
  • Blockages in the vent’s small hose

Also, the power vent can stop functioning when you install your heater in a moisture or high-humidity area. 

How To Fix:

To fix the troubles mentioned above, follow the easy resolving ways below:

  • Clean the dirt in the power vent and remove the blockage from the small hose in the vent
  • Replace the lousy pressure switch 
  • Install your heater in the average humidity or dry area

5. Burner Issue

After three successive trials, when your heater fails to establish the burner ignition mainly due to the burner hitches, the “Failed Ignition Lockout” occurs. The main burner-related problems start with the corroded burner ground wire.

Due to the damaged wiring connection, the burner fails to receive the necessary electric power to ignite your water heater. Also, the other culprits for this hitch are an improperly adjusted burner and a faulty or dirty burner.

How To Fix:

Start by checking the burner and its wiring connection on your Rheem water heater. If there is any damage sign on the burner ground wire, you must replace it. Make sure the burner is producing a stable flame. 

Next, visually inspect the position of the burner. In case it is improperly aligned, we recommend you adjust it correctly. And as a general maintenance rule and clean the burner.

6. Lousy Gas Valve

The gas valve malfunction is another major factor responsible for failed ignition lockout in your water heater. The gas valve lets the pilot be ignited. And the thermocouple gets heat from the lit pilot. 

rheem water heater lousy gas valve

But the lousy valve interrupts the heating process of your heater by closing the gas supply. You can’t expect your heater to run with the gas shut off. 

Without gas, your heater will fail to ignite. Sometimes it happens that you forget to start the manual gas shut-off valve. And that’s why the unit can throw the code. 

Furthermore, also for the following reasons, the gas valve stops working:

  • Clogged valve 
  • The glitch in the safety circuit
  • Bad electronic gas ignition components 

How To Fix:

Start the fixing process by inspecting the gas valve on your heater. Make sure the valve is in the On position and functions perfectly. Visually inspect the valve for damage or dirt on it. 

If you find it dirty, clean it. And in case it’s become damaged, you must replace it. Also, you must remove the glitch from the safety circuit for the smooth operation of your heater. And finally, verify and replace the lousy electronic gas ignition components.

7. Dirty Spark Electrode

The filthy spark electrode can cause the ignition lockout condition in your water heater. 

Due to the lack of proper maintenance and consistent use, carbon builds up around the electrode. And it makes the electrode dirty and non-functioning.

How To Fix:

Using steel wool, clean the spark electrode of your Rheem water heater. Also, follow a regular cleaning routine so that dirt can’t build in it.

8. Flame Sensor Malfunction

The flame sensor prevents harmful gas buildup in your water heater. And this device confirms that the gas valve remains open only in the presence of fire. 

The malfunctioning flame sensor fails to create a current of electricity when the gas is ignited. And thus, your heater goes into the failed ignition lockout mode. 

rheem water heater flame sensor

However, the factors responsible for flame sensor malfunction are:

  • The faulty or dirty flame sensor itself
  • High electricity variation

How To Fix:

The straightforward way to solve the above trouble is to check the sensor, clean its dirt, and replace the malfunctioning sensor. Also, take steps to prevent high voltage variation. 

How To Clean & Replace Your Rheem Water Heater Flame Sensor

To clean and replace the fire sensor of your Rheem water heater, follow the step-by-step instructions below:

Step 1: Turn off your water heater using the ON/Off switch. Or you can shut off the circuit breaker from the main electrical panel. 

Step 2: Then remove the front cover of your water heater and locate the white color flame sensor. A single wire is attached to the sensor.

white color flame sensor

Step 3: Disconnect the wire by pulling it out of its terminal. Pull hard and make sure the spade connector is not stuck in it. 

loosen the fire sensor's screw

Then, use a flat-head screwdriver to loosen the screw of the fire sensor. After that, take out the sensor. And, in a safe place, keep the screws.

pull out the sensor

Step 4: Now rub the sensor with white paper or emery cloth to clean its carbon deposit. 

Afterward, to install the new sensor in the burner hole, insert the new one. Then tighten the screws of the sensor, and push the sensor wire connectors.

9. Disconnected Connectors

The properly plugged temperature sensor connectors, igniter connectors, and other connectors ensure the flawless operation of your heater. When any connectors become unplugged, your water heater can display the ignition failure code.  

How To Fix:

The recommendation is to inspect the position of all the connectors in your heater. If you find any connector is unplugged, plug it back in immediately. 

Also, visually check the connectors and their wiring for damage. And you must replace the bad one. 

10. Clogged Blower

The pressure switch on your heater verifies whether the blower is functioning perfectly. 

However, a dirty or faulty pressure switch or clogged inducer also causes an ignition lockout. Dirt accumulation on the blower over time damages it and makes it non-functioning.

How To Fix:

Check and replace the bad pressure switch & malfunctioning blower on your Rheem water heater.

How To Reset Rheem Water Heater

You must first reset your Rheem water heater when it goes into the lockout mode and starts flashing the 6 1 or 6 5 error code. Resetting helps to take the unit out of lockout mode. Anyway, the quick resetting steps are:

 water heater's red reset button
  • Find the red reset button by removing the panel and insulation of your Rheem water heater. 
  • After finding the reset button, press and hold it until your heater make the clicking sound
  • Once you hear this sound, leave the red button. And the reset on your heater is done.


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

The pilot light keeps going out on your heater mainly due to the filthy thermocouple, loose wiring connection, improper fuel supply, etc.

Why is my Rheem water heater not heating?

Your Rheem heater is not heating mainly due to the failed power supply source, Off safety switch, and damaged circuit breaker. Also, the other responsible factors are blown fuses, defective igniting components, loose wire connections, etc.

When should I replace my Rheem water heater?

You should replace your Rheem water heater when its lifespan is over, the heater’s age is more than 10 years, or it becomes completely dead.

Wrap Up

Hopefully, all the major factors that caused your Rheem water heater to fail ignition lockout are crystal clear to you. Following the above comprehensive guide, you can now fix all these problems yourself.  

However, if you face your Rheem water heater related to any other issues, you can comment and let us know. Our experts will guide you soon.

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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