Navien Tankless Water Heater Problems 

Did you check Navien tankless water heater problems before purchasing?

Tankless water heaters are a popular solution due to the many advantages they offer over standard heaters. However, every brand has its own issues.  Even products from the best brands can experience some issues from time to time.

As long as you can fix them and they are not too common, this shouldn’t be a problem.

Still, it’s helpful to understand some common problems and to know how to fix them without immediately giving money to the plumber.

While most of these errors can be fixed and detected by consulting with your Navien tankless water heater manual.

We’ve included all the error codes and explanations, as well as guides on fixing what you can fix on your own.

Common Navien Tankless Water Heater Problems

Maybe you already know what’s causing problems with your water heater. If you don’t, the error codes should indicate what’s the issue.

Either way, here’s how to detect and repair most water heater problems:

  1. Flow Sensor

The flow sensor is a part of the device that controls the water flow. This is what ensures the tankless water heater is able to heat the water to the temperature you want it to be. Navien flow sensor problems are some of the more common issues, and they are usually caused by a clogged or rusted sensor.

If you’re experiencing issues with a flow sensor, the usual course of action is to remove the clogs and to descale your tankless water heater.

Of course, you should turn off the device before you do anything else. Remove any buildup you notice around the flow sensor. You might need to loosen the clasps beforehand.

You can follow this video, if you want to try to replace it on your own.

  1. Control board


Another common issue is a faulty control board. You’ll know that it’s malfunctioning as you’ll see it not displaying anything or by displaying wrong information.

Most of the time, this will require replacing the entire control board. Still, before you do this, you should complete the first step we’ve mentioned and reset the unit. Many times, this will solve the issue.

If resetting doesn’t work, there is nothing you can do but call a professional and ask them to install the new control board. Technically, you can purchase a new board on your own, but most people are not able to properly install it on their own, as this is a rather demanding process.

  1. Heat Exchanger

Heat exchanger is another part of the heater that can go wrong. This is a part of the unit that ‘exchanges’ gas for heat and warms the water up, without getting in direct contact with water. It is one of the more important parts of the device.

If you notice Navien tankless water heater goes cold all of a sudden, chances are you are having issues with the heat exchanger. Unfortunately, this is another issue you shouldn’t deal with on your own.

Fixing a broken heat exchanger can be a tough task, and if anything goes wrong you are risking damage to not just your heater but also to yourself. The heat exchanger works with harmful gas, and you should always leave this to the professional.

  1. No Hot Water

The heat exchanger is not the only part that warms the water up. There are several more components that are a part of this process. This includes the internal thermometer.

In fact, you should double-check the temperature settings. Chances are you’ve set the wrong temperature without noticing it.

Either way, unfortunately, this is yet another moment when you should contact a professional. It can be hard to identify the exact cause of the issue, and you should call someone who knows what they are doing to help you out.

Why people choose Navien?


A tankless water heater is a handy unit that is quickly starting to replace standard heaters with tanks. This heater can provide you with warm water without creating a ruckus and occupying too much space in your bathroom, which is why it’s so popular.

Navien is a brand famous for producing some of the best tankless water heaters on today’s market. It produces high-quality units that rarely experience any issues.

Related: Is Tankless Water Heater Worth It

Navien Tankless Water Heater Troubleshooting

As with every other unit, Navien users might end up experiencing some issues that can be considered fairly common with this model. This doesn’t mean that everyone will experience all or any of these problems, but if any problems ensue, chances are it’ll be one of these issues.

Some common Navien tankless water heater problems many users complain about include:

Resetting Navien Tankless Water Heater


Before we go into more depth about every individual Navien tankless water heater problem, there is one thing you can do whenever you notice there is something wrong with your water heater, and that is to reset it.

Many home devices can greatly benefit when you reset them. In fact, this is the first step you should do when you notice minor issues. A reset can fix most problems, and even if it doesn’t, you don’t have much to lose. Either way, it’s worth a shot.

Fortunately, Navien is one of the easiest units when it comes to resetting. While the exact process depends on the model, most units have a reset button located on the front control panel right below the main power button.

All you need to do is to hold the reset button, wait around two minutes, then turn the device back on. No matter if you were experiencing Navien NR-180 or Navien NPE 240a problems, this should solve the issue.

If it didn’t, below is our guide on fixing most problems.

Navien Heater Error Codes

While we’ve listed some of the most common water heater problems that can occur with Navien water heater, there are many more that you might also encounter. From tankless water heater no water coming out to water taking too long to heat up, many errors can happen with any model of a heater.

Luckily, Navien units have error codes on their display. These can help you identify the issue without calling a professional for help.

Here are some common Navien tankless water heater error codes you might find useful:

  • Error Code E003: Ignition failure in your heater. Most of the time, this means you need to make sure the main gas supply valve is opened properly.
  • Error Code E004: False flame detection. This means that the electrical cord isn’t properly grounded. You should be able to fix this on your own.
  • Error Code E012: Flame loss. This can indicate two things: Your electrical cord isn’t properly grounded, or the air filter is broken or dirty. Inspect both components and make sure they are in proper condition.
  • Error Code E016: Overheated heat exchanger. Most of the time, it’ll be enough to turn off your water heater for 30 minutes and to restart it. If this isn’t enough, inspect and clean the cold water inlet filter. You might also need to flush the tankless water heater.
  • Error Code E030: Exhaust overheating. Your heater should turn off if the flue temperature exceeds [2] 149oFahrenheit or 65
  • Error Code E046: Abnormality in limit control. You’ll need to call technical support at 1-800-519-8794 for this one.
  • Error Code E047: Abnormality in exhaust thermostat. This is another one that you should call technical support first.
  • Error Code E060: Abnormality in dual venturi. Also call technical support.
  • Error Code E109: Abnormality in the fan motor. Most of the time, it should be enough to inspect the intake air filter and clean it if it’s necessary.
  • Error Code E110: Abnormality in air pressure. This might mean there are some obstructions in the exhaust pipe. Maybe you’ll need to clean it. Also, clean the intake filter if you see that it is too dirty.
  • Error Code E407: Thermistor open or shortcircuited. In other words, you’re having problems with the hot water outlet. Call technical support for this one.
  • Error Code E421: Thermistor open or short-circuited. Unlike with E407, this means you’re having issues with the cold water inlet 1. You should call technical support.
  • Error Code E432: Thermistor open or short-circuited. On this occasion, you’re having issues with the cold water inlet 2.
  • Error Code E434: Abnormality in water adjustment valve. Unfortunately, you’ll need to call technical support.
  • Error Code E438: Abnormality in circulation pump. The best way to solve this is to check whether all return and water supply lines are open. Also, make sure that the 2-way valve is pointed in right directions.
  • Error Code E439: Abnormality in flow sensor. This means your flow sensor is flawed. Contact a professional.
  • Error Code E441: Thermistor is open or shot-circuited. This is similar to the previous thermistor problems, but this time the issue is in hot water inlet 2.
  • Error Code E445: Abnormality in bypass mixing valve. This is yet another issue that should be fixed by calling a professional.
  • Error Code E515: Abnormality in PCB. The best way to deal with this is to make sure your grounding and electrical cord are in good order.
  • Error Code E517: Abnormality in DIP switch setting. Call technical support to fix this.
  • Error Code E593: Abnormality in front panel key. Try resetting the device. If this doesn’t work, call a professional.
  • Error Code E615: Abnormality in input and memory. Check the power outlet. If everything seems normal, contact technical support.
  • Error Code E736: Abnormality in cascade communication. Unfortunately, the only way to fix this is to contact technical support.
  • Error Code E740: Abnormality in outdoor temperature sensor. Call a professional who will check whether your temperature sensor needs replacing.
  • Error Code E760: Flushing/service alarm. This means you haven’t flushed your heater for a while and that it’s time for regular service.
  • Error Code E782: Abnormality in main panel communication. This is an electrical issue that requires professional help.
  • Error Code E785: Abnormality in flow switch/sensor. If resetting doesn’t work, call a professional.

Related: Rinnai vs Navien Water Heaters Compared

Final Word

Tankless water heater problems can happen to anyone.

The biggest reason behind them is improper maintenance or irregular servicing.

All water heaters should go through annual flushing, and you should have a professional check them out every year or two. These are high-quality heaters that aren’t likely to break any time soon.

If any of these heater issues happen to you, try resetting the device before you call technical support. However, if this doesn’t work, your best option is to contact a professional, as only a few of these issues can be solved by a person without experience.

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