Rheem Water Heater Failed Ignition Lockout [Reasons + Solutions]

The major reasons for the Rheem water heater failed ignition lockout include a defective flame sensor, unplugged connectors, broken igniter, lack of airflow in the burner chamber, and corroded spark electrode. 

Plus, defective ignition control module, bad thermocouple, blocked heater venting, and malfunctioning gas valve are mostly responsible for causing such locked-out ignition failure in a water heater.

rheem water heater

Read through the below article to get a well-proven troubleshooting guide to resolve failed Ignition Lockout error from the Rheem water heater.

Rheem Water Heater Failed Ignition Lockout [9 Easy Solution]

Before moving to the detailing part, let’s have a glimpse at the below highlighted all the probable reasons behind failed ignition lockout with the instant solutions:

Note: You can also read how to fix Rheem water heater chamber sensor failure/9 flashes.

Probable ReasonsPossible Solutions
No Spark At Spark Electrode Clean carbon builds up around the electrode. Replace the corroded electrode
Loose ConnectorsEnsure the tighten connectors and wiring connections.
Broken IgniterReplace the faulty igniter
Broken Or Corroded Burner Ground WireReplace the damaged ground wire
No Air Flow Into The Burner ChamberVacuum up the burner chamber
Flame Sensor IssuesClean the flame sensor. Replace the defective flame sensor
Bad ThermocoupleReplace the bad thermocouple
Defective Rheem Ignition Control ModuleReplace the worn-out ignition control
Malfunctioning Gas ValveReplace the defective gas valve
Gas Shut-offEnsure the gas-shut-off valve is in the on position
Blocked VentingClean the blockages from the exhaust vent & air intake

What Does “Failed Ignition Lockout” Mean In Rheem Water Heater

Failed ignition lockout is mainly a condition of the water heater when the burner unit fails to ignite after three successive trials. There are about nine consecutive heating cycles in each trail. 

what does “failed ignition lockout” mean

When the first ignition cycle fails, the control finishes the ignition sequence and energizes the gas valve. During this cycle, the blower remains energized. Also, due to the inter-purge duration, the system is being purged. 

After the purge duration, the blower turns off and lets the pressure switch open. When the switch opens, the blower turns on again and closes the switch. 

This time, the control waits 30 minutes and attempts ignition again. When unsuccessful, the control waits for another 30 minutes and attempts ignition again. After the third unsuccessful ignition cycle, the control goes failed ignition lockout and throws an error on display.

How To Fix Error Code Ignition Lockout On Rheem Water Heater

You can easily deal with the failed ignition lockout error on your Rheem water heater like a professional if you know the actual reasons with the right solutions. 

Here, we will explore all the responsive factors behind this issue with easy fixes. Keep scrolling!

1. No Spark At Spark Electrode

The Rheem water heater’s failed ignition lockout is most likely related to the sparking issue at the spark electrode.

After pressing the igniter button repeatedly, the electrode should produce a spark to light the primary gas burner. 

If the spark is weak or there is no spark at all, there could be any of the following reasons:

  • Loose wiring connection 
  • Clogged pilot line
  • Carbon builds up around the electrode
  • A broken electrode

Follow the below methods to test the igniter and to verify the spark at the igniter:


First up, turn off the gas supply. Inspect the igniter and check for spark. If there is no spark, be sure the electrode is clogged. Clean the tip of the electrode with an abrasive material such as emery cloth or steel wool. 

Make sure there isn’t dirt, rust, or other debris clogging the pilot line. If all troubles fail to prove well, and still there is no spark, it is sure faulty or broken electrode is the culprit. 

Replace the faulty spark electrode with the help of a professional.

2. Unplugged Or Loose Heater Connectors

Loose wiring or connector is one of the most common reasons for ignition lockout in the water. There are some major connectors, including an igniter connector, burner tube, and sensor wiring connection to the gas valve.

loose heater connectors

All should be plugged in properly for a fluent water heater operation. In the case of a loose or unplugged connection, you may get the error code ‘ignition failure’ on display. 


Visually inspect the connectors of the water heater. Unplug the connectors and plug them back in again. 

Ensure all the connectors are plugged up. Replace the damaged ones

3. Defective Igniter

At times, failed ignition lockout occurs due to a faulty igniter of your water heater. The core function of the igniter is releasing intermittent high-voltage sparks through an electrode to ignite the gas. 

defective igniter

If the igniter fails, there will be no spark, and the burner will not light, which leads to the ignition lockout.

Anyway, your water heater igniter may fail due to any of the following reasons:

  • Soot or dirt build-up in the igniter
  • Broken or damaged igniter itself
  • The igniter is not getting adequate voltage

To troubleshoot the igniter issue, follow the ways below:

How To Clean & Replace Igniter In Water Heater

Cleaning & replacing the broken igniter will be easy as long as you will follow the below DIY methods:

replace igniter in water heater

i). Inspect The Burner Assembly:

 First, unplug the water and shut off the gas supply. Remove the burner access cover and disconnect all the wiring connections to the control valve. Then, pull the burner assembly.

ii). Remove The Old Igniter

Detach the grommet, and push the wire through the burner cover. Take a Phillips head screwdriver and remove the mounting screws securing the igniter to the burner tube. Pull the damaged igniter from the connection. 

iii). Clean The Igniter

You will find the dirt or soot build-up in the igniter. Take an emery cloth and clean the soot build-up. Once cleaning is done, you need to test the igniter electrically using the multi-meter. 

If the igniter does not get the voltage needed, you need to replace the defective igniter. 

iv). Install The New Igniter:

Take the new igniter and align it to the connection point. Then replace the mounting screw and ensure a secured connection. 

Place the grommet in place. Reassemble the burner assembly and connect all the wires to the control valve.

That’s all!! You have replaced the faulty igniter.

4. Burner Issues

Most of the time, the Rheem water heater goes to “failed ignition lockout” because of malfunctioning of the burner. The burner of your water heater may fail due to several reasons. Rusted or damaged burner ground is the root one among them. 

 burner assembly

Due to damaged wiring connections, the burner doesn’t get the electric power that is needed to ignite the heater. Other major reasons behind burner failure include:

  • Improperly adjusted burner assembly
  • Dirt and debris clogging the burner chamber


In the first step, visually inspect the burner chamber and check the wiring connection to see any damage or sign of burn. Replace the corroded burner ground wire.

Then, remove the burner assembly from the unit and observe if there is any clogged dirt and debris.  Take a brush-attached vacuum cleaner and clean the burner chamber. Ensure a proper adjustment of the burner assembly after cleaning. 

5. Faulty Flame Sensor

Every water heater features a sensor inside the combustion chamber known as a flame sensor. The sensor is an essential part of the heater ignition system. 

flame sensor

When it fails to continue its normal operation, the pilot light will not be lit, affecting the complete ignition system. 

As a result, the water heater’s heating unit automatically shuts down and goes to the failed ignition lockout error.

However, the flame sensor goes bad due to the following 3 major reasons:

  • Stuck dirt and debris in the sensor
  • Loose connection of the flame sensor in the combustion chamber
  • The broken or damaged flame sensor itself

However, in this stage, we will walk you through how you will deal with the defective flame sensor:

How To Clean & Replace Flame Sensor On Rheem Water Heater

To clean or replace the faulty flame sensor, follow each of the steps described below:

clean the flame sensor

Step 1: First, unplug the power connection and shut off the gas shut-off valve. Remove the front access cover and disconnect all the attachments with the gas control valve. 

Step 2: Remove the screws of the burner assembly and slide it out carefully. Now locate the flame sensor and disconnect the sensor’s screws on the burner tube using a flat-head screwdriver. Take out the flame sensor. 

Step 3: Take 400-grit sandpaper and rub the sensor to clean its carbon deposit. Wipe down the loose dirt using a soft cloth. 

Step 4: Now, take a close look at the flame sensor. If it is broken, bent, or damaged, be sure it is in non-working condition. You need to replace the faulty flame sensor. 

Step 5: Take the new sensor and install it in the burner tube. Ensure a secured placement by tightening the sensor’s screws. Finally, reassemble the burner assembly and turn on the water heater.

6. Bad Thermocouple

After completing maximum ignition attempts in the water heater, you may experience an ignition lockout due to a bad thermocouple. The water heater, with standing pilot lights, features a small device named a thermocouple. 

 bad thermocouple

The main function of the thermocouple is converting the heat from the burning flame into a small electrical current which works as a switch to open the gas valve. 

If the thermocouple fails, it won’t sense the flame, interrupting the ignition system. This will lead your Rheem water heater ignition lockout mode. 

There are a few signs of a bad thermocouple:

  • Specks of dirt accumulate on the thermocouple 
  • Incorrectly lined or positioned thermocouple
  • A kinked or broken thermocouple


To deal with the defective thermocouple, follow the below methods:

  • Turn off the gas supply first. Remove the burner assembly manifold cover to access the combustion chamber. Now, remove the manifold/burner assembly from the thermocouple.
  • Then, locate the thermocouple from the manifold cover plate. Slowly pull and twist the old thermocouple from its mounting bracket.
  • You will find carbon or dirt build-up on the thermocouple body. Clean it first using sandpaper and scrub off all the dirt.
  • Now, if you notice that the thermocouple is broken or kinked, it is confirmed that the device is faulty. Replace it. 

Note: While installing the new thermocouple, make sure it is fully seated or clicks into place. Also, place the tip of the thermocouple in the proper position.

7. Defective Ignition Control Module

The faulty ignition control module is another major reason for the Rheem gas water heater’s failed ignition lockout.

ignition control module

Each heater is equipped with an ignition module which is an essential part of the ignition system. 

The ignition control may fail due to any of the following reasons:

  • Loose or damaged control wiring harness
  • Improper alignment of the ignition control 
  • The worn-out or damaged ignition module.

When ignition control loses its integrity and inconsistency, the Rheem water heater will turn off automatically and goes to ignition lockout failed error.


Check all the wiring connections of the ignition control board. If all the wiring is secured and undamaged. But still, if the issue remains, it is sure the control board gets defective. 

The only solution is to replace the controller. If replacing the control board seems tough to you, let a professional handle the task.

8. Rheem Water Heater Venting Issues

Improper venting is one of the major reasons for ignition failure in the water heater. The water heater needs a fresh air supply for combustion and to continue the ignition systems properly. 

Anyway, if anyhow, the combustion gasses fail to move out through the vents, the ignition process interrupts and will lead to the ignition lockout. 

Note down the possible reasons relating to venting issues:

  • Blocked exhaust vent or air intake
  • Clogged condensate drainage system
  • Blocked or detached pressure switch hose
  • Broken pressure switch
  • Clogged inducer fan motor or blower
  • Dirty power vent


  • First up, clean out the blockage of the air intake vent and exhaust vent.
  • Then, get access to the inducer fan assembly and unclog the stuck debris of the fan and fan motor.
  • Clean the condensate drain line using vacuum suction or a wire coat hanger. Also, clean the build-up dirt or debris from the power vent.
  • Now, inspect the pressure switch and look for a kinked switch hose. Replace the cracked hose.
  • Also, replace the broken pressure switch. 

9. Malfunctioning Gas Control Valve

Most of the time, due to a defective gas valve, you will experience failed ignition lockout even after Rheem water heater maximum ignition attempts. The gas valve mainly controls the gas flow to the unit and allows the pilot to be ignited.

malfunctioning gas control valve

If the gas control valve fails, it won’t ignite the pilot because of no gas flow. The gas valve might be clogged by fuel residue, or the damaged gas valve itself is the culprit. 

Go through the below section to get the solutions for your Rheem water heater gas valve problem. 


First, check the gas valve if it is blocked by debris. Clean the gas valve properly and remove its clog. After cleaning, turn on the gas shut-off valve clockwise and ensure it’s in the on position. 

In the case of a defective gas valve, you have to replace it. Contact a professional if you are mechanically inclined.

How To Reset Rheem Water Heater Locked Out Ignition Failure

The ignition lockout error occurs mainly from the failed burner ignition after 3 successive trials. You have to follow the above troubleshooting steps to erase the error from your water heater. 

reset button on the thermostat

The next step is resetting the lockout condition. For instance, you have to do the followings:

Step 1: The Rheem water heater equips a reset button located on the upper thermostat. First, remove the access panel by unscrewing the two screws.

Step 2: Then, remove the insulation and plastic protective cover that sits over the thermostat. Now locate the red button on the thermostat.

Step 3: Keep pressing the red reset button momentarily to reset the lockout condition.


Why is my Rheem electric water heater not heating?

Glitches in the power supply are the root reason behind the electric water heater not heating. Either the fuse has blown, or a circuit breaker is tripped. Otherwise, the heating might get faulty which needs replacement. 

Why does my water heater keep going into vacation mode?

If your water heater keeps going into vacation mode, that means the clogged or damaged flame sensor is the root culprit. Sometimes, cracked flame sensor insulation or faulty gas valve are the leading reasons for this issue.

Bottom Lines

The Rheem water heater failed ignition lockout problem occurs due to many reasons. It is considered one of the big problems in the Rheem water heater. 

To solve this major problem, we have discussed the 9 reasons and the corresponding effective solutions. We are hopeful that this article will help you enough to solve the water heater failed ignition lockout problem easily.

Nevertheless, still, if you have any more queries, let us know in the comment box. We will try to solve the problem as soon as possible.

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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