Rheem Tankless Error Code Troubleshooting

Updated
Categories Water Heating
Want to know what the error code displayed on your Rheem tankless means? Look here.

Has your Rheem tankless water heater suddenly stopped working? Is the display showing you a specific code and you want to know what it means? We’ve got you.

Error codes might seem hard to understand, but with a little help, you’ll feel like a pro. Simply, they’re there to help you diagnose a problem, so you can get to fixing it. Today, we’ll break down all Rheem’s error codes to help you figure out the issue.


Rheem Error Code Breakdown

Rheem water heater error codes are pretty easy to understand. They’re generally displayed on the unit itself, on the screen.

However, some models require you to install an app on your phone where you’ll receive the updates. Consult your owner’s manual for exact directions on where you need to look.

Be cautious

Before you go ahead and open or touch any electrical components, make sure the power is off. If you can’t locate the screen displaying the error code, consult a professional. Touching any wires while the power is on can lead to an electric shock.

Error Code No Code

What It’s Telling You

  • Flow rate or maintenance error: When water flows through the unit, nothing happens. The control board will display the temperature, but the unit isn’t heating any water.

The Solution

  1. Adjust flow or temperature: Try to increase either the flow rate or the temperature.
  2. No crossings: Make sure that the cold and hot water lines don’t cross.
  3. Check for mistakes: Ensure there aren’t any plumbing mistakes such as crossovers.
  4. Wash the inlet water filter: Remove the filter and wash it under running water.
  5. Check the flow sensor: Ensure that it’s working properly. It might be jammed.

Error Code P1

What It’s Telling You

The Solution

  1. Check the flow from the hot water tap: You may need to clean the aerator.
  2. Wash the inlet water filter: Remove the filter and wash it under running water.
  3. Adjust temperature or flow rate: Raise the flow rate or increase the temperature.
  4. Inspect the flow sensor: Ensure the flow sensor works properly. Only do this if you know maintenance requirements are met.

Error Code 1L

What It’s Telling You

  • Maintenance issue: There’s a build-up of limescale and scale deposits.

The Solution

  1. Flush the heat exchanger: Consult your owner’s manual for exact instructions.
  2. Adjust altitude settings: If you installed the unit at a higher altitude, make sure that the proper settings are in place.

Error Code 05

What It’s Telling You

  • Maintenance warning: There could be a blockage in the vent exhaust or the air intake. The unit will still operate.
  • Installation warning: The vent pipes may not be properly connected to the vent terminal. The unit will still operate.

The Solution

Option 1
  1. Clear the vent: Remove whatever it is that’s blocking the vent.
  2. Check vent installation: Ensure that venting was done according to installation requirements.
  3. Inspect the fan motor: If you meet the maintenance requirements, check the fan motor for errors.
Option 2
  1. Check the vents: Ensure that all vents are sealed accurately and meet venting requirements.
  2. Inspect blower motor: If maintenance is up to date, check the blower motor.

Error Code 10

What It’s Telling You

  • Maintenance error: Blower motor not working properly.

The Solution

  1. Clear the vents: Unblock any blockages in the venting system as well as the blower motor and air intake.
  2. Inspect blower motor: If maintenance is up to date, check the blower motor for flaws.

Error Code 11

What It’s Telling You

  • Gas supply or installation error: Ignition failure.

The Solution

  1. Make sure that the gas pipe is open: Turn the valves to the “On” position.
  2. Check the gas type, pressure and volume: Make sure they match the requirements of the unit.
  3. Empty the gas line: Bleed out all the air from the gas line.
  4. Check the size: Make sure the gas line, regulator and meter are the right sizes.
  5. Check connections: Make sure the unit is accurately grounded.

If you meet the gas supply and installation requirements, then check the following:

  1. Check the gas control valve: Ensure there aren’t any open or short-circuited wires.
  2. Make sure the igniter rod is working: Check the wiring and connections for any flaws.
  3. Ensure there’s no damage: Check the wiring for the ignition rod for any damage.
  4. Check the control board: Make sure that it’s working properly. Check the wiring and connections.
  5. Check the status of the flame rod: Make sure it isn’t blocked.

Error Code 12

What It’s Telling You

  • An issue with the gas supply, installation or lack of maintenance: Flame failure.

The Solution

  1. Check gas type and pressure: Make sure that they’re accurate. Consult your owner’s manual for the required gas type and pressure.
  2. Empty gas line: Bleed the air from the gas line. Consult a professional if you don’t feel comfortable doing it yourself.
  3. Check the wiring: Make sure the wires to the flame rod are connected.
  4. Check for carbon buildup: Inspect the flame rod and make sure there’s no carbon buildup.
  5. Check the sizes: Be sure that the gas line, regulator and meter are the right sizes.
  6. Inspect the wiring: Ensure that the unit is accurately grounded.
  7. Check the power supply: Is the unit receiving enough voltage or does it drop? If it drops, consult an electrician.
  8. Restart the wiring harnesses: Disconnect and reconnect the wiring harnesses on the gas control valve as well as the control board.

If maintenance isn’t the issue:

  1. Inspect the circuits: Check for short circuits in the gas valves.
  2. Check for any damages: Look in the wiring harness to the flame rod.
  3. Check the PCB: Consult your owner’s manual or call a skilled technician.
  4. Ensure the flame rod’s status is accurate: Consult the owner’s manual for exact instructions.

Error Code 13

What It’s Telling You

  • Indoor venting: Flame rod warns of poor or improper combustion.

The Solution

  1. Check installation requirements: Make sure that the intake and exhaust vents meet the requirements for safe operation. Consult your owner’s manual.

If you meet the vent requirements:

  1. Unblock the vents: Remove blockage from the venting or what’s in front of the vent termination.
  2. Check altitude settings: Double-check that the altitude settings are correct. Consult your owner’s manual.
  3. Check the flame rod: Ensure that it’s working as it should.
  4. Examine the blower motor: Look for blockages or broken parts.

Error Code 14

What It’s Telling You

  • Condensing units only: Maintenance error: Flue pipe overheating.
  • Mid-efficiency and condensing units: Fault in the overheat limiter (OHL).

The Solution

Option 1
  1. Unblock heat exchanger: Clear the heat exchanger from any blockage.
  2. Unblock blower motor: Clear out any blockage from the blower motor or vent.
Option 2
  1. Check the “U” connector: Ensure the “U” connector is accurately connected to the control board.
  2. Inspect wiring harness: Make sure it’s properly connected to the OHL.
  3. Inspect the heat exchanger: Ensure there are no cracks or separations.
  4. Check the overheat wrap: If there’s a failure, the unit should be replaced.
  5. If your unit is a condensing model: Check the thermal overload sensor.

Error Code 15

What It’s Telling You

  • Maintenance: Heat exchanger overheating — boiling safety device. The heat exchanger exceeded 207 degrees Fahrenheit for more than 15 seconds.

The Solution

  1. Flush the heat exchanger: Clear it for lime or scale build-up. Consult the owner’s manual for exact instructions.
  2. Check the inlet valve: Ensure that it’s completely open.
  3. For commercially used units: Lower the temperature below 180 degrees Fahrenheit if you’re at a high altitude.

If maintenance is up to date:

  1. Inspect the thermistor: It should be in the heat exchanger.

Error Code 16

What It’s Telling You

  • Maintenance: The outlet water is above the preset thermostat setting.

The Solution

  1. Examine the heat exchanger: Ensure that it isn’t clogged.
  2. Eliminate any airflow restrictions: Make sure there’s enough air surrounding the unit and vents.

If maintenance is up to date:

  1. Examine the thermistor outlet: Check for any issues.
  2. Inspect the heat exchanger thermistor: Consult the owner’s manual for instructions.
  3. Check the gas valve: Ensure that it works properly and isn’t clogged.

Error Code 24

What It’s Telling You

  • Operational switch malfunctioning.

The Solution

  1. Restart the unit: Turn the water off, disconnect the remote control and try again.
  2. Check connections: Ensure that the unit is electrically grounded.
  3. Reset the unit: Try to press the “MIN” and “MAX” button on the control board to reset the unit.

Error Code 29

What It’s Telling You

  • Condensing units only: Maintenance error: Clogged neutralizer.
  • Mid-efficiency and condensing units: Maintenance error: Temperature in the heat exchanger is too low.

The Solution

Option 1
  1. Check that the drain line isn’t blocked: Ensure that you removed the shipping cap.
  2. Clear out: Clean the neutralizer drainage ports on the inside of the unit. Clean the outside neutralizer drainage lines.
  3. Clean the air inlet screen: Remove it and wash under running water.
  4. Wash the heat exchanger fins: Consult the owner’s manual.

If maintenance is up to date:

  1. Check the water inside the neutralizer: Measure the electrode’s water level.
Option 2
  1. Clean the air inlet screen: Remove it and wash under running water.
  2. Clean the heat exchanger fins: Consult the owner’s manual.

Error Code 31

What It’s Telling You

  • An issue with the inlet thermistor.

The Solution

  1. Check the wiring: Inspect the wires of the thermistor for any damage.
  2. Check for scale in the thermistor: If so, consult the owner’s manual on how to clean it.
  3. Ohm out the thermistor: Consult the owner’s manual.

Error Code 33

What It’s Telling You

  • An issue with the outlet thermistor.

The Solution

  1. Check wires: Ensure there’s no damage in the thermistor wiring.
  2. Check for scale in the thermistor: Clean it if there is, but consult the owner’s manual for instructions.
  3. Ohm out the thermistor: Consult the owner’s manual.

Error Code 34

What It’s Telling You

  • Issues surrounding the thermistor, such as wiring.

The Solution

  1. Check the wiring: Ensure there’s no damage in the thermistor wiring.
  2. Ohm out the thermistor: Consult the owner’s manual.

If there are no issues with the wiring and readings are normal:

  1. Ensure there’s enough space: Make sure there are no airflow restrictions around the unit and in the vent terminal.
  2. Inspect the fan blade: Check that it sits tightly on the motor shaft but is still capable of spinning freely.

Error Code 35

What It’s Telling You

  • The connection to the thermistor is incorrect.

The Solution

  1. Check connections: Ensure all thermistors are fixed to the right connections on the control board.
  2. Check connectors: Make sure that all the quick connectors between the thermistor and control board are correct.

Error Code 51

What It’s Telling You

  • Problem with the gas control valve.

The Solution

  1. Inspect terminals: Check for any loose or broken terminals to the gas control valve wiring.
  2. Ohm out the gas control valve: Consult the owner’s manual.

Error Code 52

What It’s Telling You

  • There’s an issue with the PGFR (proportional gas flow regulating) valve.

The Solution

  1. Check the wiring harness on the PGFR valve: Ensure there aren’t any loose or broken connections.
  2. Ohm out the PGFR valve: Consult the owner’s manual.

Error Code 61

What It’s Telling You

  • Maintenance error: Blower motor.

The Solution

  1. Check blower motor: Ensure that it can turn freely. There should only be a little restriction.
  2. Check the motor wiring harness: Look for damaged or loose connections.
  3. Check the length of the venting: It shouldn’t exceed the maximum length. If so, it’s likely bent.

Error Code 72

What It’s Telling You

  • An issue with the flame rod: False flame detection.

The Solution

  1. Inspect the flame rod: Make sure it touches the flame as the unit fires.
  2. Check for any blockages: Ensure the inside of the burner chamber is clear.
  3. Check all the wiring: Be sure there’s no damage or loose connections.
  4. Examine the voltage: Ensure the right voltage is coming through.

Error Code 82

What It’s Telling You

  • Control board isn’t programmed correctly.

The Solution

  1. Check the chip: Ensure that it’s installed correctly.

Error Code 99

What It’s Telling You

  • Blower motor isn’t venting.

The Solution

  1. Check the blower motor: Clear any blockages.
  2. Check if the heat exchanger is blocked: Consult the owner’s manual on how to unblock.

Why Your Tankless Often Requires a Reset

If you often find that your tankless requires a reset, it might be that it’s overloaded. Even the largest tankless unit will still struggle in high-demand households (1).

You can, of course, continue to reset it every time. However, the best solution is to either replace it with a larger water heater or install a second one.

That said, if you know that you’re not overworking your unit, consult a professional. It might be another issue with the heating elements.

Why Do Water Heaters Have a Reset Button?

Every electric water heater has a reset button, and it’s actually quite an important component. The reset button is there for safety reasons. It will trip as soon as the water is heated to extreme temperature.

There are a couple of reasons that the reset button might trip. These are:

  • Faulty thermostat: The thermostat isn’t working properly, causing the water to overheat.
  • Loose connections: A loose electrical wire is a potential fire hazard. Hence the reset button will trip if it senses an issue with the wiring.
  • A poor heating element: If the heating element is faulty, it could continue to send an electrical current through the unit even after you’ve closed the tap.

How to Re-Light Your Rheem Tankless Water Heater

Fortunately, this process is easy, and you can always have a look in the owner’s manual. But here are some steps:

  1. Place gas knob in the “Off” position: Turn the knob clockwise until it reaches the “Off” position.
  2. Set thermostat to lowest temperature: Turn the temperature dial counterclockwise to the lowest setting. Wait at least 5 minutes for the gas to pass through.
  3. Remove the outer door: After lifting the outer door off, turn the gas knob back to the “Pilot” position.
  4. Press the ignitor: To the left side of the gas knob, there should be a red button. Hold that down while you press the piezo ignitor striker that’s located to the right side of the knob. Continue pressing down until it’s lit — check through the viewing window.
  5. Rotate the gas knob: Turn it counterclockwise to its “On” position and then set the temperature.

No More Errors

Tankless water heaters are like computers that are programmed to heat water in an instant (2). With so much technology, errors do happen from time to time. Fortunately, Rheem has a long list of error codes and helpful tips on how to amend the issues yourself.

Which error code is your Rheem tankless water heater displaying? Please let us know in the comments below. Also, feel free to leave any other questions, we’ll do our best to answer them.

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About the Author

Peter Gray

Peter has been a homeowner for 35+ years and has always done his own repair and improvement tasks. As a retired plumber, Peter now spends his time teaching others how they can fix leaks, replace faucets, and make home improvements on a budget.
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1 Reader Comment

  1. Furman Broome

    My Rheem tankless water heater will run a minute and kick off putting out the 13 code. I unplugged it and now it is giving a 2, 13, 76, 1 codes. My unit is 2 years old!

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