Installation Guide
43 Page
Troubleshoong
Owner's Guide
Remote Green LED
Malfunction
description
Diagnosis
651
Four Flashes
Flow adjustment 
valve fault (Only 
Easy-Link & Multi-Unit 
System)
 Inspect the flow adjustment valve (Part #402), for  
connection/breakage of wires, locked motor drive due to 
scale buildup, and/or water leakage.
661*
Four Flashes
Bypass valve fault
(510C model only)
 Inspect the bypass valve (Part #403), for connection/
breakage of wires, locked motor drive due to scale 
buildup, and/or water leakage.
701*
One Flash
Computer board fault
 Check for connection/breakage of wires (Part #713).
711*
One Flash
Gas solenoid valve 
drive circuit failure
 Refer to the 111 and 121 error codes.
721*
Six Flashes
False flame detection  Check if condensate drain is installed on the vent collar of 
the water heater.
 Check if there is leaking from heat exchanger (Part #401).
741
N/A
Miscommunication 
between water heater 
and remote controller
 Check the model type of the remote controller.
 Inspect the connections between the water heater and 
remote controller.
 Check the power supply of the water heater.
751
N/A Miscommunication 
between water 
heater and built-in 
controller
 Inspect the connections between the water heater 
and built-in controller.
 Check the power supply of the water heater.
761
N/A
Miscommunication in 
Easy-Link system
 Check if the connections between the parent unit and the 
child units are correct. Refer to p. 25.
991
Five Flashes
Imperfect 
combustion
 Check the gas type of the water heater.
 Inspect the environment around the water heater. 
Determine how long the unit has been installed.
 Check the altitude/elevation of the area of where the 
water heater is installed.
 Check if there is any blockage in the intake air and/or 
exhaust. 
 Check to make sure that there is enough distance between 
the concentric vent terminal and other exhaust vent ter-
minals.
 Check if there is grease and/or dirt in the burner (Part 
#101) and the fan motor (Part #103), especially if the 
water heater has been installed in a contaminated area.
*These error codes will be cleared when water flow stops.










