DIY Error Codes

Navien NPE-2 tankless water heater Error E109

The fan motor is not running as expected. Navien's listed action: clean the air intake filter.

Clean the air intake filter. If E109 comes back, call a pro.

Start the fix →When to call a pro ↓
Full answer & models

Navien E109 on the NPE-2 means: abnormal operation: fan motor. Clean the air intake filter. If E109 comes back, call a pro.

Applies to: NPE-180A2NPE-210A2NPE-240A2NPE-180S2NPE-210S2NPE-240S2
Also searched as: Navien error E109, Navien E109, Navien error code 109, Navien 109 code

Gas appliance. Power off and let it cool before any maintenance.
Why
If you smell gas: do not try to light any appliance, do not touch any electrical switch, and do not use any phone in your building. Leave and call your gas supplier from a neighbor's phone; if you cannot reach them, call the fire department. Navien: turn the water heater off and disconnect the power supply before maintenance. It can stay hot for several minutes after it is turned off; wait until it cools to avoid burns. Water at or above 125 °F (52 °C) can cause instant scalding, severe burns, or death.

What E109 means

The fan motor is not running as expected. Navien's listed action: clean the air intake filter.

More detail
Navien's error-code chart (section 5.2) lists E109 as "abnormal operation: fan motor". If the listed remedies do not resolve the problem, Navien says to contact Technical Support.

5-minute checks

Fix it step by step

Step 1 of 2

  1. Clean the air intake filter

    • 20 min
    • Screwdriver, Toothbrush
    • DIY

    Safety: Gas appliance. Power off and let it cool before any maintenance.

    Power off, unplug, remove the front cover, take out the filter (top left), wash and dry it.

    More detail

    Clean the air intake filter.

    Navien section 4.5: press Power to turn the heater off, disconnect the power supply, remove the front cover, remove the screw holding the air intake filter (top left), pull it out, separate it from the plastic assembly, clean it with a toothbrush and clean running water, let it dry completely, then reassemble, replace the cover, reconnect power and turn it on. Navien recommends cleaning this filter every 3-4 months.

    Did the code clear?

  2. Call a licensed pro

    • Decision
    • None
    • Pro decision

    Stop here and book a qualified technician.

    More detail

    Call a licensed pro.

    If E109 returns with a clean filter, the fan or controls need a licensed technician.

    Still showing E109?Need a pro → call a pro

Code cleared. Nice work.

Watch the display for a day to make sure it stays clear.

Back to top

Fixed after any step? Watch the display for a day to make sure it stays clear. Still E109 after step 2? call a pro.

Call a pro if…

  • E109 returns with a clean air filter.
  • You hear grinding or unusual fan noise.

FAQ

What does Navien E109 mean?

Abnormal operation of the fan motor, per the NPE-2 chart. The listed action is to clean the air intake filter.

Source: Navien NPE-2 User's Information Manual (NPE-A2/NPE-S2), Section 5.2 Understanding Error Codes, Sections 4.2-4.5 Maintenance. Written by the DIY Error Codes team. Updated 2026-10-16. DIY Error Codes is independent and not affiliated with or endorsed by Navien.