If you're looking for help fixing your Navien Water Heater, look no further! Our comprehensive Navien Water Heater error code guide will explain common issues, provide tips, and show you how to read your model's error codes.

CODE: E003 
PROBLEM: Ignition failure in your tankless water heater. 
FIX: Confirm the main gas supply valve is open. 

CODE: E004 
PROBLEM: False flame detection. 
FIX: Confirm properly grounded electrical cord. 

CODE: E012 
PROBLEM: Flame loss. 
FIX: Confirm properly grounded electrical cord. Inspect and clean intake air filter. 

CODE: E016 
PROBLEM: Overheated heat exchanger. 
FIX: Turn off the water heater for 30 minutes and restart. Inspect and clean the filter in cold water inlet. Flush the heat exchanger. 

CODE: E030 
PROBLEM: Exhaust overheating. The unit will shut down when the temperature in the flue exceeds 149° Fahrenheit (65° Celcius). 
FIX: Turn off the water heater for 30 minutes and restart. Inspect and clean the filter in cold water inlet. Flush the heat exchanger. 

CODE: E046 
PROBLEM: Abnormality in limit control. 

CODE: E047 
PROBLEM: Abnormality in exhaust thermostat. 

CODE: E060 
PROBLEM: Abnormality in dual venturi. 

CODE: E109 
PROBLEM: Abnormality in fan motor. 
FIX: Inspect and clean the intake air filter. 

CODE: E110 
PROBLEM: Abnormality in air pressure. 
FIX: Confirm there are no obstructions in the exhaust pipe. Inspect and clean intake air filter. 

CODE: E407 
PROBLEM: Thermistor open or short circuited (hot water outlet). 

CODE: E421 
PROBLEM: Thermistor open or short circuited (cold water inlet 1). 

CODE: E432 
PROBLEM: Thermistor open or short circuited (cold water inlet 2). 

CODE: E434 
PROBLEM: Abnormality in water adjustment valve. 

CODE: E438 
PROBLEM: Abnormality in circulation pump. 
FIX: Confirm all water supply and return lines are open. Check direction of the internal 2-way valve. 

CODE: E439 
PROBLEM: Abnormality in flow sensor. 

CODE: E441 
PROBLEM: Thermistor open or short circuited (hot water inlet 2). 

CODE: E445 
PROBLEM: Abnormality in bypass mixing valve. 

CODE: E515 
PROBLEM: Abnormality in PCB. 
FIX: Confirm proper grounding of electrical cord. 

CODE: E517 
PROBLEM: Abnormality in DIP switch setting. 

CODE: E593 
PROBLEM: Abnormality in front panel key. 

CODE: E615 
PROBLEM: Abnormality in input and memory. 

CODE: E736 
PROBLEM: Abnormality in cascade communication. 

CODE: E740 
PROBLEM: Abnormality in outdoor temperature sensor. 

CODE: E760 
PROBLEM: Flushing/service alarm. 

CODE: E782 
PROBLEM: Abnormality in main panel communication. 

CODE: E785 
PROBLEM: Abnormality in flow switch/sensor.

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