Sunday, December 18, 2016

Navien tankless water heater: Error code 38

My Navien tankless water heater (model 240A) stopped working all the sudden. After opening the cover, I found code 38E displayed on the control board. However, this error code was not found in the operation manual.

According to Navien's FAQs:
"I have no error codes on my remote, yet my unit will not produce hot water. What should I do?

The issue is most likely the flow sensor inside the unit is not spinning properly.

We recommend opening and closing the pressure relief valve (should be located near the outlet of the unit). Depending on amount of debris affecting the flow sensor, this may help temporary. We recommend contacted your original installer or an NSS to service the sensor."

I also found this 38 error code listed here mentions checking the water flow sensor. Based on various forum discussions, it seems to be the root cause for others who experienced the same error as well.

Luckily, it is not too difficult to take it apart and check the water flow sensor. Thanks to youtuber Tredsaw12 who created this step-by-step guide, I was able to extract the water flow sensor. If this is your first time working with the water heater, I would suggest you first check this video by Skobel Homes to get a better understanding of it.

After taking out the sensor, try shaking it. You should hear some noise as there's a small gear inside. If not, it's probably stuck which caused the failure. Check if there's any blockage inside and clean it. Try running water through it. Also try blowing air through it with your mouth. You should feel the gear inside is spinning.

And then, you just need to reverse the process and put it back together. Hopefully your water heater will start working again. If not, you may need to replace the water flow sensor and/or call a professional for further inspection. Good luck!

Update (2017-05-29):
It has been almost 6 months now. I would say the method above is a temporary solution. After cleaning the water flow sensor, the 38E error would come back after a few weeks. After 4-5 times, I decided to put an end to all this. I replaced it with a new sensor (you should look up the right model for your water heater). It has been going strong for months. No more 38E :)

Navien Tankless Error Codes
FAQ | Navien
SIMPLE - Navien tankless FLOW SENSOR replacement -- 10 minute job - YouTube
How to maintain your tankless hot water heater - YouTube


Unknown said...

Thanks for compiling this information, very helpful! Personally, there isn't enough service information provided with tankless water heaters, at least that was my experience. My 6-year-old NR-240A quit on the weekend with E038. Once the flow control valve was removed I found compressed air on the propeller freed it up enough, and a drop of olive oil as well! Hoping it will tie me over until the new part is here. In the meantime, hot water is flowing!

Unknown said...

Thank you. Just had a error code 38E on my 10 year tankless which is not listed in the manual. Changed out the water flow sensor (#52 in the manual diagram) which solved the problem.

joninthesprings said...

After 5yrs without issues, our NR-240A quit while Error Code 038E was displayed on its thermostat. Purchasing a replacement Navien Flow Sensor but, in the mean time, managed to successfully restore the water heater to full function after 30-minutes of maintenance: 1) unplugged & switched off, 2) closed inlet & outlet, 3) removed cover & flow sensor with bucket under unit to catch small amount of water, 4) blew into sensor, 5) sprayed CLR into it, 6) rinsed, 7) poured a teaspoon of olive oil in sensor, 8) reattached, 9) unscrewed/rinsed/re-installed both water filters located adjacent to inlet/outlet valves, 10) re-attached cover, 11) opened inlet & outlet valves, 12) plugged unit back in and switched on. Minimal air spurt thru faucet afterwards, then our hot water was working again (better than it has in a long time).

just me_again said...

Unfortunately, for me,this issue seems to come back after some time. I've replaced the flow sensor twice as well as replaced my circulation pump. Still, this issue returns. I've literally taken this whole water heater apart and cleaned out each link but still I have issues with it. I'm to the point where I'm considering just having a regular old water heater installed. This tankless has been nothing but problems and I've only had it for about 6 years. A plumbing company quoted me $6k to install a newer model. Crazy

Babai said...

Just came across this post while grappling with my 10 year old NR 240 A tankless with external recirculation.

When I turn the hot water on, no flow detected, when I set the recirculation timer and reset the unit, error 38 comes on. Took apart the flow sensor, looks good, no buildup inside.

Changed the DIP Switch 2 setting to recirulation OFF (switches 4,5 down), no effect, recirculation is off, but still no water flow detected when hot water tap is turned on.

Any pointers highly appreciated.

Chuckmartel said...

Any luck just me again? I have the same issue. Replaced a burnt out pump and flow sensor. Code 38 at start up. Pump tries but not enough flow to trip the flow sensor. Turned off the dip switch so the pump doesn’t burn out.

Walker34 said...

I also saw error code 038 upon trying to fire up my NR-24A after over a week without gas supply. After shutting off the inlet valve, I removed the flow sensor and disconnected the plastic pipe with the impeller inside. (The quick-clips made this easy, but be prepared for some water to spill.) I ran some compressed air through the pipe and dropped some canola oil into the small impeller inside. After hooking everything back up, the unit fired up and is working just fine. I have a new part on the way from Amazon ($23), but hopefully this will last until the package arrives. Easy fix!