E109 Moderate Moderate DIY

Navien Tankless Water Heater E109 — Fan Motor Abnormal Operation

Navien Tankless Water Heater · Error code E109

What E109 Means

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

Symptoms

  • E109 displayed
  • Fan runs continuously
  • Unit will not fire normally

Common Causes

1
Stuck or unbalanced fan

Debris or bearing wear causing irregular operation.

2
Wiring fault

Pinched or shorted fan harness.

3
PCB fault

Driver circuit issuing wrong command.

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.

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.

Common replacement Navien fan motor View on Amazon→

More Navien Tankless Water Heater Codes

E003 E003 — Ignition Failure E003C E003C — Cascade Ignition Failure E012 E012 — False Flame / Flame Loss E016 E016 — Overheat / High-Limit Trip E027 E027 — Gas Type Setting Error E030 E030 — Fan / Combustion Blower Fault

All Navien codes → All tankless water heater codes →

Verified against manufacturer documentation: navieninc.com

Always unplug an appliance before servicing it. This guide is for informational purposes and is not a substitute for a qualified technician.