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Navien E109 — Fan Motor Error
Your Navien flagged a problem with the combustion fan — the blower that pulls in air and pushes out exhaust. Without correct airflow, the unit can't burn safely, so it locks out.
The combustion fan controls the air side of combustion — drawing in fresh air and pushing exhaust out through the vent. Navien watches the fan's speed, and when it can't reach or hold the RPM the control board expects, it posts E109 and stops, because burning gas without correct airflow is unsafe.
The most common trigger is a dirty air-intake filter starving the fan of air. Beyond that it's the fan motor itself, its wiring, or the voltage the board is supplying. We start with the cheap, common causes before touching the fan.
What causes E109
1. Dirty or blocked air-intake filter
A clogged intake filter is the first thing to check — it starves the fan and skews the airflow the board expects. Cleaning it resolves a good share of E109s.
2. Worn or failing fan motor
Fan motors wear out after years of runtime. Bearings drag, RPM drops, and the board flags E109. Replacement is a defined repair.
3. Wiring or connector to the fan
A loose, corroded, or damaged connector between the fan and the control board can interrupt the RPM signal or power.
4. Control-board voltage
If the board isn't supplying correct voltage to the fan, the fan can't spin up. We measure at the board before deciding fan vs. board.
What you can safely check first
- Check and clean the air-intake filter. A clogged filter is the cheapest and most common cause.
- One reset is reasonable after cleaning the filter.
- Do not keep running the unit with a fan fault. Airflow is what makes the combustion safe.
When to stop and call us
If E109 returns after a clean filter and one reset, the fan, its wiring and the board voltage have to be tested with a meter. That is a professional diagnostic, not a parts swap.
Seeing E109 on your Navien?
Book online and we will diagnose the actual cause, explain what we find, and price the repair before starting.
Navien E109 FAQs
What does Navien error code E109 mean?
E109 is a combustion fan motor error. The fan moves air through the burner and pushes exhaust out the vent; when it cannot reach or hold the speed the control board expects, the unit locks out because burning gas without correct airflow is unsafe.
What causes E109?
The most common cause is a dirty air-intake filter starving the fan. Beyond that it can be a worn fan motor, a loose or corroded wiring connector, or the control board not supplying correct voltage to the fan.
Can I fix E109 myself?
You can safely check and clean the air-intake filter and try one reset. If the code returns, the fan, its wiring, or the board voltage needs to be tested with a meter — that is a professional diagnostic. Do not run the unit repeatedly with a fan fault.
How much does E109 repair cost?
The $99 service fee sends a licensed technician out to diagnose the problem. Approve the repair on the spot and the fee is not charged at all; decline it and the $99 covers the visit. If it turns out to be a filter or connector, the fix is inexpensive; a replacement fan motor is a defined part-and-labor cost we quote before proceeding.
Other codes on this unit? See all Navien error codes.
Why South Shore homeowners choose Johnson Bros.
Navien E109 diagnosed properly
We diagnose the cause rather than clearing the code and hoping. You get an upfront price before any work starts.
Not sure what's wrong? Send a photo or videoBooking online is the quickest way to hold the next open appointment. Call instead if it is urgent and you would rather talk to someone.
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Navien E109 diagnosed properly
We diagnose the cause rather than clearing the code and hoping. You get an upfront price before any work starts.
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