Abnormal operation: fan motor Manual reset
The E109 error code on Navien boilers indicates abnormal operation: fan motor manual reset. Symptoms include the system checks the rpm signal after the fan starts to run, and displays the error message 109e (cleared, combustion, and the boiler switches into lock-out. (however, the air volume sensor should be normal.).
Navien E109 means: abnormal operation: fan motor manual reset. The usual causes are 4. if the fan connector is wet due to any reason including leakage, take corrective action by powering the or defective rotator. You can safely reset the boiler once — if E109 returns, do not keep resetting. A qualified heating engineer should diagnose the root cause.
What Does E109 Mean
The E109 code is shown by the boiler’s control board when it detects abnormal operation: fan motor manual reset. The boiler then stops instead of continuing to run in that condition: the code is the appliance reporting a problem, not proof that the boiler is broken.
| What you see on the boiler |
|---|
| The system checks the RPM signal after the fan starts to run, and displays the error message 109E (cleared |
| combustion, and the boiler switches into Lock-Out. (However, the air volume sensor should be normal.) |
Common Causes
Causes documented in 23 technical sources.
| Cause |
|---|
| 4. If the fan connector is wet due to any reason including leakage, take corrective action by powering the |
| Defective rotator |
Safety Warning
E109 involves electrical or pressure-related components. Do not attempt repairs without proper qualifications. Ensure the boiler is electrically isolated before any inspection. If you notice water leaks, unusual sounds, or pressure anomalies, contact a qualified heating engineer immediately. Out (gas valve and ignition transformer locked). (However, the air pressure sensor should be normal.)
Parts & Prices
Prices shown are indicative. Actual prices and availability vary by region.
Step-by-Step Diagnosis
1. Listen for the fan — it should start before ignition. If silent, check power supply to the fan motor. 2. Spin the fan manually (with power off) — if it feels stiff or gritty, the bearings are worn. 3. Check the wiring connections between the fan and PCB. 4. Test the air pressure switch — with the fan running, the switch should close. Disconnect and test with a multimeter for continuity. 5. Check the flue for blockages — inspect the full length including the terminal. 6. Verify the condensate trap is clear. 7. Measure the fan speed signal at the PCB (Hall sensor output)
How to Fix It
Replace the fan motor assembly if bearings are worn or motor is not running
replace the air pressure switch if it is stuck or reading incorrectly
clear any flue or condensate blockage
repair or replace damaged wiring
if PCB is not providing the signal, replace the PCB
Refer to the Navien service documentation for the detailed procedure. Only a qualified engineer should carry out these repairs.
Diagnostic Tools
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Affected Models
Navien models that can display fault code E109:
| Model Family | Output Range | Frequency |
|---|---|---|
| All Navien models | — | Possible |
Frequently Asked Questions
Replace the fan motor assembly if bearings are worn or motor is not running. According to the technical documentation, this is the first check on the list for E109.
E109 is not classified as a high-severity fault, so the boiler can be reset once. If E109 comes back, stop resetting: the underlying cause is still there and needs a qualified heating engineer.