Navien NPE-2 Code E109
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.
Call a proThe verdict
Call a licensed plumber
Clean the intake air filter — that is Navien's own instruction and it costs nothing. If the code stays, this is a fan motor in the combustion air path, which means the unit opened with power and gas off. A motor is a real part at a real price.
Typical cost: $0–$900
US estimate for parts and labor. Prices vary by region and by who does the work — see how we estimate costs.
What the manual says
The meaning above is transcribed from the manufacturer's diagnostic documentation for the NPE-2 — not averaged across the brand.
Source: Navien NPE-2 User's Information Manual (p. 17), read Aug 2026 — the manufacturer's own documentation for this exact series.
What you can safely check
Before anything else: if you smell gas, stop here, leave, and call your gas utility.
- Clean the intake air filter. Navien's listed remedy for this code, and free.
- Note whether you heard a rattle or whine before it failed — that points at the blower wheel or bearings.
- If the code returns, turn the unit off and book a licensed professional.
Frequently asked questions
Why would a dirty filter cause a fan motor code?
The board watches whether the fan reaches the speed it asked for. A restricted filter changes the load on the fan, and a fan that cannot hit its target reads as a fan fault even though the motor is fine.
Code E109 on other Navien series
The same code number can mean something different on another series — make sure you're reading the page for your exact unit: