Rheem Tankless Water Heater Error Codes [The Complete Guide]

This is a complete guide on Rheem Tankless Water Heater Error Codes. In this guide, we will describe the common error codes this tankless water heater displays. Besides, we will also depict those reasons that trigger the error messages and provide the solutions as well. So, let’s get started right here.

Table of Contents

13 Common Rheem Tankless Water Heater Error Codes

Rheem tankless water heater starts malfunctioning over time. When there is any problem with the unit, it will pop up an error code on the display. It helps us diagnose and determine the exact problem with the water heater. From this chapter, you can learn about the most common error codes the tankless water heater shows. We also break down how to clear those error codes from the display. So, keep reading. 

01. Rheem Tankless Water Heater Error Codes P1

Your Rheem tankless water heater will trigger the P1 error codes if there is a lack of sufficient water flow to activate the unit. If the inlet screen at the cold water connection gets clogged with dirt & debris, the water will not flow through it. Besides, your water heater will throw the error code ‘P1’ if the water flow sensor goes bad. 

How To Fix: 

Hire a plumber and tell him to clean the inlet filter at the cold water connection to the unit. On the other hand, if you want to save money, check out this video to learn how to clean the inlet filter. 

After cleaning the inlet filter, run the hot water only in the tap to check. If the water doesn’t flow, we recommend you increase the flow rate. Otherwise, you should replace the water flow sensor. Watch the following tutorial to learn how to replace the water flow sensor. 

02. Rheem Tankless Water Heater Error Codes C7

The error code c7 stands for a defective communication between the remote control and the tankless unit. Your Rheem Water Heater will trigger this error code due to a faulty remote control, a bad PCB, and a damaged wire connection between the tankless unit and the remote. 

How to Fix:

Start with inspecting the remote control. To check the remote control, unplug your water heater from electricity and pull out its cover. Then, locate the two terminals connected with the remote control. 

Next, disconnect the wiring from the remote control and plug your water heater into an outlet. If your water heater comes on, we bet the culprit is the remote control itself or the wiring between the remote control and the tankless unit. 

Now, you may ask- how can I determine whether the suspect is the remote control or its wiring? Attach the remote control to the tankless unit with a different wire. If the remote control works, we bet the wiring is at fault. Otherwise, you should replace the remote control with a new one. 

If you fail to start the water heater after replacing the remote control or its wiring, we are 100% sure the culprit is the PCB or control board. Replacing the control board is the only solution to fix this water heater issue. 

03. Rheem Electric Tankless Water Heater Error Code E4

An error code ‘E4’ on your Rheem Tankless Water Heater indicates that the flow meter sensor gets faulty. The flow meter sensor is also referred to as a water temperature sensor. If this sensor is at fault, it will not send a signal to the computer, which starts the tankless unit. 

A defective flow meter sensor, broken wire, and poor connection are the culprits that trigger the error code E4. Below, we will show you how to fix those issues to clear away the error message. 

How To Fix: 

We recommend you check for a broken wire or poor electrical connection. If there is any damaged wiring, your water heater will be unable to send a signal to the control board. Once you repair the damaged wiring, run the hot water tap to see whether the unit works or not. If not, you should replace the flow meter sensor or the flow control valve of your Rheem Tankless Water Heater. 

04. Rheem Electric Tankless Water Heater Error Code E5

The water heater will trigger the error code E5 if there is too much water flow. Apart from these, defective combustion systems, problems with the main burner or pilot, and faulty motor are other culprits responsible for throwing this error code. 

How To Fix:

Begin with slowing down the flow rate of your water heater. 90% of the time, this troubleshooting step will help to eliminate the warning message from the control panel. Just turn off the water supply valve to slow down the flow. 

Secondly, inspect the exhaust vent or air intake pipe for a clog. If they get blocked by dirt, debris, and carbon buildups, this may cause a problem with the combustion. Don’t forget to release the blockage if needed. Also, make sure you tidy up the air inlet filter, combustion air fan, and heat exchanger fan. 

Lastly, check the fan motor for proper operation. If needed, replace it with a new one. 

05. Rheem Tankless Water Heater Error Code 10

According to Rheem, the error code 10 will pop up when the fan motor fails to create sufficient ventilation. Also, this warning message indicates that the unit has detected a false flame. Your tankless water heater will display this wrong message if the venting system fails or doesn’t work properly. 

How To Fix: 

We recommend you check the heat exchanger fins first for blockage. If the heat exchange fins get clogged, release the blockage. Then, inspect the heat exchanger flapper valve and make it move freely at the vent connection of your water heater.  

Afterward, remove every speck of dirt, debris, and buildup from the air intake filter. Ensure you eliminate every obstruction from the vent termination of the building and the flapper valve. 

06. Rheem Tankless Water Heater Error Code 11

Insufficient fuel or restricted gas flow, faulty gas solenoid valves, defective igniter wire harness, and a problem with the igniter are some caveats that trigger the error code 11. When this error code will pop up, understand there is no ignition on your tankless water heater. 

How to Fix: 

First off, make sure there is enough fuel in your gas tank. If it’s empty, don’t forget to fill it with gas. Also, make sure the gas flow valves are open and they don’t get clogged with dirt or residue buildups. 

Then, inspect the gas solenoid valves and make sure they work properly. Now, you may ask- how can I understand whether the solenoid valves function correctly or not? Simple. If the igniter and the fan function but the main burner doesn’t, we bet one of the gas solenoid valves doesn’t work properly. 

Lastly, ensure the igniter wire harness is intact. We recommend you check out this in-depth guideline on Rheem Tankless Water Heater Code 11. We broke down everything that will help eliminate the error message from the control panel. 

07. Rheem Tankless Water Heater Error Code 12

Error code 12 means your tankless water heater fails to detect the flame. Your Rheem Water Heater will pop up this warning message due to the following reasons: 

  • Dirty flame sensor
  • Insufficient gas supply
  • Improper inlet gas pressure
  • Gas lines too small for the BTU load
  • A defective gas control valve
  • Clogged venting
  • Defective flame rods and heat exchanger

How To Fix: 

Addressing and fixing those issues we mentioned will help you eliminate the error code from the display of the unit. We recommend you read our in-depth guide on Rheem Tankless Water Heater Code 12. In that article, we described everything that causes your water heater to trigger the error message 12. Also, we broke down the troubleshooting steps to clear the message. 

08. Rheem Tankless Water Heater Code 13

When the ODS gets activated, your tankless water heater will trigger the error code 13. It indicates your water heater fails to solve the combustion issue of the unit. In plain words, the water heater error code 13 stands for a defective combustion system. Several reasons are responsible for the heater to throw this error message. They are dirty or defective flame rods, faulty ODS thermocouples, and incorrect burner manifold pressure. 

How To Fix:

To erase the error code 13, start with cleaning the dirty flame rods. You can use 100-grit sandpaper to remove the carbon buildup from the flame rods. 

Next, inspect the ODS thermocouple to see whether it functions properly or not. A clogged heat exchanger, venting system, and air intake filter are responsible for making the ODS thermocouple defective. Just release blockage from those components to get the ODS thermocouple back in the working condition. 

And lastly, check out the burner manifold pressure. If it’s incorrect, you should adjust it. We have an in-depth guide on Rheem Tankless Water Heater error code 13 where we broke down the way of adjusting burner manifold pressure. 

09. Rheem Tankless Water Heater Code 14

Error code 14 on tankless water heater means the Overheat Film Wrap sensor has activated. If this sensor senses that the heat exchanger of your water heater gets overheated, it will pop up this error message. Improper fuel type, rusty or defective heat exchanger, and faulty Molex connector are some caveats responsible for triggering this error code. 

How To Fix: 

Most tankless water heaters are operated by natural or LP gas. It will be best to check the manual and use the fuel type recommended by the manufacturer. Secondly, take your eyes on the heat exchanger to see whether it gets dirty or not. If yes, clean the heat exchanger. Finally, ensure the Molex connector is in good condition. To learn more about error code 14, read this in-depth guide.

10. Rheem Tankless Water Heater Error Code 29

In the troubleshooting manual, Rheem says that error code 29 stands for too low heat exchanger outlet temperature. A clogged air inlet filter, dirty heat exchanger fins, and bad heat exchanger thermistor are some culprits behind this issue. 

However, there is also another meaning of the error code 29. It indicates a neutralizer drainage failure. This neutralizer is specially designed to keep the drain condensate away from the water heater. If this drainage system gets clogged, your tankless water heater will flash the error code 29 to prevent the burner from being flooded. 

A clogged condensate drain line and incorrect condensate line piping are the common causes to block the drainage system. Nonetheless, freezing weather can also block up the neutralizer drainage system. 

How To Fix: 

Begin with cleaning the air inlet filter. Then, inspect the heat exchanger fins for a clog and release the buildup. 

Next, check the resistance of the heat exchanger thermistor. The resistance of connector R between #Black3 and #Yellow5 wires will be 4K to 10K ohms. If you don’t get this reading, you should replace the heat exchanger thermistor. Otherwise, you need to change the PCB. 

On the other hand, you should get a neutralizer kit and install it on your water heater if the neutralizer drainage fails. Installing the kit on the water heater, will treat the condensate properly for safe disposal into the drain. Ensure the condensate flow is free of dirt, debris, and buildups. On top of this, you must ensure the drain will not allow backflow. 

During winter & freezing days, we recommend you insulate the drainpipe by using a heat tape. It will be better if you install the heat tape close to the exit to the main drain to get the best output. 

Read Details: Rheem Tankless Water Heater Code 29

11. Rheem Tankless Water Heater Error Code 61

The error code 61 popping up on the LED display represents a faulty blower motor. Here faulty means either the blower motor itself gets defective or its housing gets clogged with dirt or debris. 

How To Fix: 

What I recommend to you first is to clean the blower motor and its housing. But this task requires a lot of elbow grease. So, I highly recommend you to call a professional to handle this. 

However, if you are mechanically inclined, keep scrolling. 

First off, turn the unit off at the remote controller or at the circuit breaker. 

Then, remove the front access panel. From the bottom of the unit, take out two screws that hold the computer bracket in place. 

Remove those two screws from the bottom
*Remove those two screws from the bottom*

Next, you need to remove some wires that come in the way like the blower motor wire, flame rod wire connectors, over wrap film plug, and others. 

Afterward, take out these two screws from the top of the computer board. 

unscrew these two screws that hold the computer board

Tilt down the computer board, which will reveal the blower motor. 

Tilt down the computer board to expose the blower motor

Now, remove the three side screws of the blower motor and take out the blower motor. And this is how the blower motor looks like: 

blower motor on rheem tankless unit
*Blower motor on Rheem tankless unit*

Inspect the blower motor for broken fins or dirt or debris that gets stuck inside it. If needed, clean the inside of this motor.

Also, don’t forget to check the breather box for debris and use a vacuum cleaner or a lightly damp rag to clean the box. 

the breather box
*The Breather Box*

Of course, don’t hesitate to replace the blower motor if it gets broken. 

Once you clean or change the blower motor, follow the steps in reverse to reinstall the blower motor.

12. Rheem Tankless Water Heater Code 65

Water volume control fault is what error code 65 indicates. A defective or loose wire connection between the water control and the connector B on the PCB is the main culprit that causes your heater to pop up with this error message. Besides, faulty water control assembly is another reason responsible for flashing the error code 65. 

How to Fix:

As a basic inspection, start with verifying that there is water flow through the unit. Next, access maintenance information to determine the flow rate.  

Afterward, measure the voltage of the wiring between the water control and the connector B. The voltage should be 8 to 16 VDC. If you don’t get this reading, you must replace the PCB. 

If you get the voltage reading, take another measurement at connector B between the White#2 and White#8 wires. If you don’t get the appropriate voltage reading (8 to 16 VDC), you should replace the water control assembly. 

13. Rheem Tankless Water Heater Code 76

Error code 76 on Rheem Tankless Water Heater is an indication of faulty communication with the remote control. Your water heater will flash this error message on the control panel due to: 

  • Loose remote control wiring or the remote control itself gets defective
  • A bad filter capacitor

How To Fix:

Firstly, determine whether there is a problem with the remote control wiring or the remote control itself. If you don’t know how to detect the source of the problem, you can read this guide. We also broke down what you should do if the capacitor gets faulty. 


What does E5 mean on my Rheem tankless water heater?

E5 on a Rheem Tankless Water Heater means there is a high flow rate. It means the desired water volume is too high that exceeds your desired preset temperature. To fix this issue, you need to slow down the flow rate. 

How do you clear the error code on a Rheem tankless water heater?

Resetting your tankless water heater will help you clear the error code from the control panel. To reset the water heater, turn off the hot tap water and the unit itself. Leave the unit for 2o minutes. Then, turn on the water heater again, which will reset the heater. If it doesn’t erase the error message, fix the issues that cause the heater to pop up the error code. Then, reset the Rheem tankless water heater again. 

What does E4 mean on a Rheem tankless water heater?

E4 on your Rheem tankless water heater indicates an issue with the flow meter sensor. If the flow meter sensor gets defective, the unit fails to send a signal to the computer that is responsible for starting the device. 

Why is my Rheem tankless water heater beeping?

Your Rheem Tankless Water Heater will beep and show an error code if there is a problem with the unit. It will alert you that your water heater requires service or that there are damaged or broken components you need to repair or replace. 


Rheem Tankless Water Heater displays a lot of error codes due to specific reasons. Those error codes don’t only help you understand the actual problem with the unit but also make it a breeze to fix them. 

From top to bottom of this guide, we broke down every error code our tankless water heater displays. So, follow the troubleshooting steps we mentioned to clear the error message. 

6 thoughts on “Rheem Tankless Water Heater Error Codes [The Complete Guide]”

  1. good stuff mate i have a rheem gas 871624pfj tankless it comes with code e 51 ,i turn unit off it clears error code and will work and stay working untill you stop using hot water then back to e51,cleaned filters ,still same any help pls.

    • Hey Don,

      The unit will throw the error code e51 if the gas inlet solenoid valve is at fault. In this case, check the followings:

      1. Inspect the gas valve wiring harnesses for loose or damaged terminals
      2. Ensure the connections to the circuit board are secure.

      Cycle your water heater two times by turning off- then turn on- at 10 seconds intervals.

      After cycling the unit if you notice any remaining flame through the view window, I bet the gas control assembly is the culprit. In this case, you must replace the gas control assembly.

      If you observe no remaining flame, don’t hesitate to check the relay connection of flame rod connector. Also, inspect the flame rod electrodes and clean them. Checking the main burner and cleaning it will also worth it.

      If nothing works for you, I suspect the PCB is the culprit.

      Hope this input will be helpful for you.


        • Hey Shelley,

          I guess the PA error code is a air conditioner related fault code. It represents a water protection fault at the indoor unit. Am I right?

  2. Receiving error code 61 -Faulty Blower Motor. Did not see that error code here. Any help you could provide or resource you can point me to would be greatly appreciated. Thanks.
    Rheem Model RTG 84DVLP

    • Hey CJ,

      I have just updated this article as per your request. Check the number 11 where I break down the error code 61. And thank you for mentioning your issues. I am glad to help.


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