Navien · Tankless Water Heater Moderate

E109 — Fan Motor Abnormal Operation

Fan operates outside the expected range — typically the fan is detected running when it should not be, or speed feedback does not match command.

Keep using it?
Yes, with caution
DIY difficulty
Moderate
Verified against
navieninc.com ↗

How to fix it

  1. Power off, inspect fan for debris or damage.
  2. Check harness routing and continuity.
  3. Reseat connectors at fan and board.
  4. Replace fan motor if mechanically failing.
  5. Replace PCB if fan tests OK and code persists.

Why it happens

Typical signs: E109 displayed · Fan runs continuously · Unit will not fire normally

  • Stuck or unbalanced fan Debris or bearing wear causing irregular operation.
  • Wiring fault Pinched or shorted fan harness.
  • PCB fault Driver circuit issuing wrong command.

Parts you may need

If diagnosis points to a failed part, these are the common replacements. As an Amazon Associate we earn from qualifying purchases.

More Navien tankless water heater codes

E003 E003 — Ignition Failure E012 E012 — Flame Loss E016 E016 — Overheat / High-Limit Trip E027 Tankless E027 — Sensor Abnormality E030 E030 — Abnormal Exhaust Temperature (Flue Overheat) E046 E046 — Abnormality in Limit Control (Heat-Exchanger High-Limit)

All Navien codes → All tankless water heater codes →

Frequently asked questions

What does the E109 code mean on a Navien tankless water heater?

Fan operates outside the expected range — typically the fan is detected running when it should not be, or speed feedback does not match command.

What causes the E109 code on a Navien tankless water heater?

Stuck or unbalanced fan: Debris or bearing wear causing irregular operation. Wiring fault: Pinched or shorted fan harness. PCB fault: Driver circuit issuing wrong command.

Is it safe to keep using a Navien tankless water heater with a E109 error?

Yes, with caution. This is rated a moderate-severity fault.

How do I fix E109 on a Navien tankless water heater?

Power off, inspect fan for debris or damage. Check harness routing and continuity. Reseat connectors at fan and board.

Always unplug an appliance before servicing it. This guide is for informational purposes and is not a substitute for a qualified technician. Verified against manufacturer documentation: navieninc.com.