A tankless water heater is a smart purchase that will provide limitless hot water for 20+ years.

Although tankless water heaters need far less upkeep and service than conventional tank water heaters, they still need to be maintained, and it’s critical to know what to do in the event of a problem.

We offer service for various brands, but for this article, we’ll concentrate on Rinnai tankless water heater troubleshooting as the self-diagnostics tool generates codes that make it simpler to identify and fix problems.

Post questions concerning alternative tankless systems (Rheem, Noritz) in the Ask Dave section, and we’ll respond as quickly as we can.

Tankless Rinnai systems have a lot of admirers here! Your Rinnai tankless water heater is a smart water heater, which means it has a self-diagnostic feature that regularly checks to see whether the appliance is operating as intended.

The device shows an error code when anything goes wrong.

You can easily identify the issue and decide whether you can repair the unit yourself or whether you need a professional to service it by using our Rinnai tankless water heater error code guide.

Error Codes for Rinnai

Burner not operating when in freeze protection mode, error code 2.

Phone a plumber.

Power interruption during bath fill, error code 3.

Lock all hot water taps and faucets.

Double-click the On/Off button.

Restart the hot water and do a test.

To reset the system, you may need to attempt this a couple of times.

Exhaust or air supply blocked, error code 10

Before contacting a plumber, you may take a number of actions.

Try these things:

  • Verify the venting material. Is it sanctioned by Rinnai? (Here are the venting materials that Rinnia has authorized.) If not, either change the venting material yourself or have a plumber do it.
  • Check for obstructions in the exhaust or input of the flue.
  • Are the venting parts attached correctly?
  • Condensation collar inspection Is it fitted correctly or is it loose?
  • Are the dip switches properly configured?
  • Is the fan turning freely, or is there anything in the way?

Call a plumber if the trouble code is still visible.

issues with the ignition, error code 11

Most folks need to contact a plumber to address this since it involves gas and gas lines.

However, the following are the actions the plumber will do (some of which you may cautiously test yourself):

  • The gas is on. Check the gas meter, cylinder, or water heater.
  • The pressure and gas type are right.
  • Is the size of the gas line, meter, and/or regulator correct?
  • Does the gas line include air? Have the lines bled of air by a plumber.
  • The dip switches must be set.
  • The appliance must be grounded.
  • Try disconnecting the EZConnectTM or MSA controllers to try to pinpoint the issue.
  • What about the igniter? Is it working well, or does the igniter need to be changed? To determine whether the problem is with the igniter or the wire harness, check it out.
  • Take a look at the gas solenoid valves. Any shorts or open circuits?
  • Inspect the burners after removing the burner covers to check that they are correctly sealed and that the burner surface is free of dirt or dampness.

If you are unable to resolve a Rinnai error code 11 on your own because you are unfamiliar with these components, wiring, and gas, you should contact a plumber.

Code 12 error: Flame failure

Most folks need to contact a plumber to address this since it involves gas and gas lines.

You might, however, cautiously test out some of the actions a plumber will perform.

Use the preceding checklist to troubleshoot Rinnai error code 11, and if it doesn’t work, try the following:

  • Check the power source. Exist any weak connections?
  • Which voltage is it? Has the voltage changed?
  • Is the wire connecting the flame rod? Any issues with the flame rod’s carbon buildup?
  • Examine the components for DC shorts.

If you are unable to resolve a Rinnai error code 12 on your own because you are unfamiliar with these components, wiring, and gas, you should contact a plumber.

Code 14 error: thermal fuse

There is an issue with the thermal fuse.

Try the following to see if you can solve it:

  • Look for obstructions to airflow.
  • Is the circulation system’s water flow low? This may result in short-cycling issues.
  • Test the dip switches.
  • Are there any obstructions in the combustion chamber? The exhaust pipe, what about it? The operation of a thermal fuse might be affected by obstructions.
  • The heat exchanger looks what? Any separations or cracks? Warm spots? Scale build-up is indicated by hot patches.
  • In accordance with the owner’s manual’s directions, flush the heat exchanger.
  • Verify the safety circuit’s resistance.

Error Code 16: Overheating of the environment

A limitation in airflow is often the root of this issue.

Examine the following for blockages or clogs:

  • Chamber for combustion
  • Exhaust pipes
  • Heat transfer

Additionally, you should look for airflow obstructions around the unit and vent terminals as well as insufficient water flow in circulating systems that might be causing short-cycling.

The issue ought to go away after the impediments are removed and the water and airflow are improved.

If not, dial a plumber’s number.

Outgoing Water Temperature Sensor Fault, Error Code 32

Examine the sensor carefully for this straightforward one.

Watch for damage and scale accumulation.

If cleaning it doesn’t work, the sensor probably has to be replaced.

Heat Exchanger Outgoing Temperature Sensor Fault, Error Code 33

Similar to what was just said.

Examine the sensor with great care.

Make sure the fan blade is secure on the motor shaft and is not damaged.

Check for damage and scale buildup.

If cleaning it doesn’t work, the sensor probably has to be replaced.

Combustion Air Temperature Sensor Fault Error Code 34

the same as before Examine the sensor and wire in detail.

Watch for damage and scale accumulation.

If cleaning it doesn’t work, the sensor probably has to be replaced.

Modulating Solenoid Valve Signal Abnormal Error Code 52

The solenoid valve has to be replaced, most likely.


  • Verify the wire harness for the modulating gas solenoid valve for loose or broken connections.
  • Measure the valve coil’s resistance.

Tightening loose terminals could help you address the issue.

Failure of the combustion fan, error code 61

Check the combustion fan for:

  • Can the fan freely rotate?
  • Are there any wire harness issues? It could be damaged or have loose connections.
  • Is the resistance of the motor winding a problem?

Water Flow Control Fault Error Code 65

For this one, you most certainly need to hire a plumber.

During the bath filling process, the water flow control valve has failed to shut off.

Cut off the water supply and stop the bath filling process right away.

then make a plumbing call.

Solenoid Valve Circuit Fault Error Code 71

The solenoid valve has to be replaced, most likely.


  • Check the solenoids’ wire harnesses.
  • Each solenoid valve coil’s resistance should be measured.

Flame Sensing Device Fault Error Code 72

Try the following first before calling a plumber:

  • Verify that the flame rod is in contact with the flame when the device ignites.
  • Check for damage on the flame rod wiring.
  • Use sandpaper to polish the flame rod.
  • Look for any dirt or sludge that may be obstructing the flame at the flame rod within the burner chamber.
  • Change the flame rod.

Scale buildup in the heat exchanger is the cause of error code 00, or “LC.”

Make a call to a plumber and ask them to replace or flush the heat exchanger.

Because it still permits the tankless water heater to function, many consumers disregard this requirement.

The LC code and temperature setting will alternately appear on the display.

Don’t disregard this code merely because it permits you to continue using the unit; doing so might lead to more severe issues in the future.

Instead, get the heat exchanger serviced.

Need Assistance with a Tankless Water Heater in the Charlotte Area?

While we have extensive expertise with various kinds of tankless (on demand) water heaters, this article will focus on troubleshooting Rinnai tankless water heaters since that is the model we install the most often.

Call us at 704.846.5371 if you need tankless water heater repair.

We are eager to collaborate with you!

Article Synopsis

Quick question and response: Why is there an error code on my Rinnai tankless water heater?

Error codes are shown by Rinnai tankless water heaters for a number of reasons.

If you encounter error code 02, it’s a good idea to hire a plumber since it signifies that the burner is not operating during freeze protection mode.

There is a temperature warning when there is an error code.

Examine the heat exchanger, exhaust pipes, and combustion chamber for blockages or obstructions.

The issue should be resolved by removing the impediment.

How To Reset Rinnai Tankless Water Heater Videos Suggestions From Youtube

How to reset a Rinnai tankless water heater after descaling unedited vid 1 – Tony Phillips
How to reset a Rinnai exterior Sensei unit with WIFI after a power outage. – That Tankless Guy
How To Reset Your Tankless Water Heater – All Things Plumbing, Heating & Air

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Written by Bob Matsuoka
Bob Matsuoka is a blogger and founder of RVing Beginner blog. He has been blogging for over five years, writing about his own family’s RV adventures, tips for people who are interested in buying an RV or taking their family on an adventure by RV.