Installation Guide
56 Page
Troubleshoong
Owner's Guide
Controller
Green
LED
Malfunction
description
Diagnosis
331
Two
Flashes
Outlet thermistor fail-
ure (540 model only)
Check for connection/breakage of wires and/or debris on therm-
istor (Part #407, 408, 411, 715).
341
Two
Flashes
Exhaust thermistor
failure (Indoor models
only)
391
Two
Flashes
Air-fuel ratio rod fail-
ure
Check for connection/breakage of wires (Part #709) and/or soot
on the AFR rod (Part #108).
441
Two
Flashes
Flow sensor failure
(Easy-Link System only)
Check for connection/breakage of wires and/or debris on the
flow sensor impeller (Part #402).
510
Six
Flashes
Abnormal main gas
solenoid valve
Check for connection/breakage of wires (Part #708) and/or burn
marks on the computer board (Part #701).
551
Six
Flashes
Abnormal gas
solenoid valve
Check for connection/breakage of wires (Part #708) and/or burn
marks on the computer board (Part #701).
611
Four
Flashes
Fan motor fault Check for connection/breakage of wires, dust buildup in the fan motor
(Part #103) and/or burn marks on the computer board (Part #701).
Check for frozen/corrosion of connectors (Part #103).
651
Four
Flashes
Flow adjustment
valve fault (Easy-Link
System only)
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
(540 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 #714).
711
One
Flash
Gas solenoid valve
drive circuit failure
Refer to the 111 and 121 error codes.
721
Six
Flashes
False flame detection For indoor models, 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 temperature
controller (Indoor
models only)
Inspect the connections between the water heater and tempera-
ture 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. 37 to 38.
941
Five
Flashes
Abnormal exhaust
temperature (Indoor
models only)
Check if the set temperature is higher than 140°F (60°C) and the
system is Recirculation.
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.
If the water heater is installed as a direct-vent system, check
whether there is enough distance between the intake air termi-
nal and the exhaust terminal.
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.