Navien tankless water heater code E109
Fan motor fault. Code E109 means the same thing on all 2 Navien series documented here — but the fix, and what it costs, is still worth reading for your exact unit.
What code E109 means on each Navien series
| Series | What it means | Verdict | Typical cost |
|---|---|---|---|
| NPE-2 | Fan motor fault | Call a pro | $0–$900 |
| NPE-A / NPE-S | Fan motor fault | Call a pro | $0–$900 |
Each row opens the full page for that generation. We hold manuals for NPE-2 and NPE-A / NPE-S, and each one gets its own reading of code E109 — what Navien documents, what you can safely check yourself, and what the repair should cost.
What each manual actually says
The table above compares 2 series in four columns, which is enough to route you and not enough to explain anything. This is the Navien wording behind each row, one entry per manual, so you can see where the 2 readings of code E109 agree and where they part company.
NPE-2 — Fan motor fault
The fan that supplies combustion air and pushes exhaust through the vent is not reporting correctly. Navien gives owners one thing to try first, and it is free: clean the intake air filter.
NPE-A / NPE-S — Fan motor fault
The fan motor is not running as expected. Navien gives one owner instruction and it is a good one: clean the intake air filter. A filter packed with lint makes the fan work against a restriction, and that is the cheap version of this fault.
Does it matter which Navien you have?
NPE-2 and NPE-A / NPE-S all route code E109 the same way: a professional, at $0–$900. That makes it one of the Navien numbers you can act on before working out which unit you own.
Which Navien do you have?
On the 2 series that report code E109, the model number on the rating label starts NPE — match yours against the 13 listed below. You can also use the full model-number decoder.
Where this comes from
Source: Navien NPE-2 User's Information Manual (p. 17), read Aug 2026 — the manufacturer's own documentation for this Navien range.
Source: Navien NPE Operation Manual (NPE-A / NPE-S) (p. 16), read Aug 2026 — the manufacturer's own documentation for this Navien range.
Parts, guides and symptoms behind code E109
Code E109 on these 2 Navien series points at 1 guide, 2 parts and 2 symptoms, each named by the manufacturer's own procedure for this code.