Navien Troubleshooting Guide (Service Manual)


For you first timers, Navien tankless water heaters are some of the best tankless water heaters on the market today, however they should not be installed by beginners, or “do it ur selfers”! These units have many aspects to their proper installation.

You don’t just hang it on the wall, tie in the gas & water lines and turn it on like you do for the cheap tankless water heaters you can get at the home depot. (Which you would want to return during the first week of winter, or during their next recall)

In my opinion these things (Naviens’) shouldn’t even by installed by anyone (even a licensed plumber) unless he or she as installed a couple of them before.

Check out this link from a Duel unit installation we did last week. 20 pictures from the job are posted here for some quality visual simulation that this post is lacking.

(Most likely you already have a Navien, had it installed by someone that didn’t really know what they were doing. You’re in a mess and read this a bit to late, and that’s why you are here! but don’t worry we’re going to help you, and do it in 30 different languages) FYI- If English isn’t your first language just go to the top right of this site, and click on “your” flag for the language that makes you feel more comfortable.

Proper gas sizing, water lines, venting, condensation, special factory requirements, and local and state code requirements for ventilation piping, permits to increase/ run new gas lines!!! are just a few but the very most important “things to remember” (Which soooooo many” plumbers” for one reason or another aren’t doing these days.)

Well what I have here in front of me is a service manual from Navien. First I’m going to list all the error codes that may be displayed on your unit’s digital thermostat or on the until itself (under the cover) and let you know what that means, and what your qualified plumber can do about it.

The Error Code Guide (1)

Error Code(s) What is happening Diagnostic & Action
E001- Water is boiling inside the heat exchanger Self-diagnostic/Action
  • Clean the inlet water filter.
  • Check the automatic flow adjustment valve.
  • Check the heat exchanger, remove and clean with a cleaning solution.
E003- Ignition failure Self-diagnostic/Action
  • Check to see if the main gas supply valve is open.
  • Check that the power is ON.
  • Check the igniter for spark.
E004- False flame detection Self-diagnostic/Action
  • Ensure ground wire is connected.
  • Check the igniter for spark.
E007- Hot water outlet. (Thermistor- open) Self-diagnostic/Action
  • Check the thermistor.
  • Replace the thermistor
E008- Hot water outlet. (Thermistor – short) Self-diagnostic/Action
  • Check the thermistor.
  • Replace the thermistor
E009- Abnormal fan motor activity Self-diagnostic/Action
  • Check and clean the air filter.
  • Check and clean the fan motor.
E010- Abnormal air pressure. Self-diagnostic/Action
  • Check the vent pipe for obstructions.
  • Check and clan the air filter.
E012- Flame loss. Self-diagnostic/Action
  • Check the main gas line (valve open?)
  • Check the intake air pipe for obstructions.
  • Check the ground wire.
  • Check power supply.
E015- Abnormal control board. Self-diagnostic/Action
  • Check power supply
  • Check the GFI.
E016- Overheating of heat exchanger. Self-diagnostic/Action
  • Turn OFF the system for at least 30 minutes then restart.
  • Clean the inlet water filter.
  • Check the automatic flow adjustment valve.
  • check the heat exchanger, remove and clean with a cleaning solution.
E021- Cold water inlet. (Thrmistor 1- open) Self-diagnostic/Action
  • Check Thermistor.
  • Replace Thermistor.
E022- Cold water inlet. (Thermistor 1- short) Self-diagnostic/Action
  • Check Thermistor.
  • Replace Thermistor.
E027- Abnormal activity of the air pressure sensor. Self-diagnostic/Action
  • Check the vent pip for obstructions.
  • Check and clean air filter.
E030- Exhaust Overheat: The Exhaust high limit switch shuts down the unit when the flue temperatures exceed 149 Fahrenheit, (65 C) Self-diagnostic/Action
  • Clean the inlet water filter
  • Check the automatic flow adjustment valve.
  • Check the heat exchanger; remove and clean with a cleaning solution.
E032- Cold water inlet. (Thermistor 2- Open) Self-diagnostic/Action
  • Check the thermistor
  • Replace the thermistor
E033- Cold water inlet. (Thermistor 2- Short) Self-diagnostic/Action
  • Check the thermistor
  • Replace the thermistor
E035- Abnormal activity of the gas pressure sensor. Self-diagnostic/Action
  • Check gas line for gas, (with gas supply “ON”)
  • Check for debris. (with gas supply “OFF” )
E036- Communication failure. Self-diagnostic/Action
  • Contact Navien tech dept.
E037- water leak inside unit. Self-diagnostic/Action
  • Close cold water main.
  • Replace leaking parts.

If any of the above solutions do not resolve the problem with the water heater, contact Navien’s Technical department at 1-(800) 519-8794.

If you’re in Fairfield, or New Haven counties in Connecticut you’re in luck. We are not quite official factory representatives yet, but we do have experience fixing these units. (Mostly due to poor installations) 9 out of 10 problems we encounter has to do with bad installations installed by bad, or better stated under qualified plumbers. The problems that we do find with the units are mostly clogged water filters, and internal valves. If their is a problem not easily fixed, it usually has to do with the computer board, and even those are fixed quickly by a Navien factory rep. Navien tankless water heaters are engineered in such a manner that replacing parts (once you know which one to replace) is quick and painless, meaning nearly every part inside and out of the unit can be fixed/ replaced.

Navien tankless water heaters are some of the best tankless water heaters on the market today. When properly installed they will save space, water, energy, money, and work as designed for 25 – 30 years with very little maintenance.

I’ve got a few emails asking basically asking me the same thing over the past few weeks that were all somewhat asking me this.

Johnny, why are you always talking about Navien, and not really much about other manufactures?

It may seem like I’m always going on and on about Navien and it’s true to some extent, but let me be clear. has not received 1 dollar from Navien. (Although I honestly do wish they would spend a few bucks on some banner ads, or to put up one of their commercials on the side bar some day soon) (Dear Navien, this page is being read at least 250- 750 times a day- the site is getting 2,500 – 4,500 visits every single day)

Anyways… The real reason is we talk about them so much, is because:

Custom Color Box

  • (1st All tankless water heaters pretty much work the same way) However Navien’s…
  • They produce the most hot water GPM (at the lowest temp rise)
  • They can handle the huge demand
  • They have the highest efficiency rating on the market 98%
  • We install at least 2 of them every week, and everyone of them is working correctly
  • We have dozens of very happy clients with Naviens
  • Exhaust pipe is PVC which is inexpensive and easy to work with. (Unlike nearly every other brand that requires very expensive double walled, Fasenseal, or B vent.) Which just one 90 degree bend cost 53 dollars!
  • THE NUMBER 1 REASON (We don’t want call backs!) We don’t want to go back and “fix” anything after we have installed it, as that has an extreme negative effect on our profits and our free time. We install Naviens because we feel they are the best, and we want to install it and never see you again. (or until your next plumbing task)

I feel that we are one of the very best plumbing companies in the business of installing tankless water heaters. For the simple fact that we install 2 – 5 a week, every week. By installing so many of them we are able to install one, and remove the old tank in one day. We also get better prices than 95% of all plumbers/ plumbing companies in our area because of the volume of units we purchase. By getting the units at lower prices, and installing them quickly, and being able to over come all if any obstacles we are able to offer prices that are regularly 500 – 1,000 lower than other local plumbing companies prices we “compete” with.

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