Navien E109: fan motor fault

The combustion fan pulls in air and pushes exhaust out through the vent. E109 means the control board has detected that the fan is not running as it should.

The meaning below comes from Navien's manuals for its NPE condensing tankless water heaters. Many codes are shared with Navien combi boilers, but check the manual for your model if something does not match.

Start with the intake air filter

Navien condensing heaters have an air intake filter, and a clogged one is the first thing the manual tells you to check for E109. Lint, dust and pet hair from a laundry room or garage clog it quickly.

1. Turn the unit off and unplug it.
2. Remove the intake air filter as shown in your manual.
3. Rinse it with water or clean it gently, let it dry fully, and reinstall it.
4. Plug the unit back in, turn it on and open a hot tap.

If the code comes back

Navien's service steps include checking and cleaning the air filter, verifying the voltage and wire connections to the fan, and checking and cleaning the fan motor. A fan that is worn, blocked or not getting the right signal from the board will need cleaning or replacement.

Prevent it

• Clean the intake air filter as often as your manual recommends, and more often in dusty spaces.
• Keep the area around the heater clear of stored items and lint.
• Check the vent terminals outside for nests and debris.

See every code on our Navien error codes page.