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Malfunction
Controller
LED
description
311*
Two
240HX3/340HX3:
Outlet Thermistor
Flashes
Failure
540HX3: Heat
Exchanger Thermistor
Failure
321*
Two
Inlet thermistor failure
Flashes
331*
Two
Outlet thermistor fail-
ure (540HX3 only)
Flashes
341*
Two
Exhaust thermistor failure
(Indoor models only)
Flashes
391*
Two
Air-fuel ratio rod fail-
ure
Flashes
510
Six
Abnormal main gas
solenoid valve
Flashes
551
Six
Abnormal gas solenoid
valve
Flashes
611*
Four
Fan motor fault
Flashes
661*
Four
Bypass valve fault
(540HX3 only)
Flashes
One
701*
Computer board fault
Flash
711*
One
Gas solenoid valve
drive circuit failure
Flash
721*
Six
False flame detection • For indoor models, check if condensate drain is installed on the vent collar of
Flashes
741
N/A
Miscommunication
between water heater
and remote controller
751
N/A
Miscommunication
between water heater
and built-in controller
(Indoor models only)
941
Five
Abnormal exhaust
temperature (Indoor
Flashes
models only)
991
Imperfect
Five
combustion
Flashes
*These error codes will be cleared when water flow stops.
• Check for connection/breakage of wires and/or debris on thermistor (Part
#407, 408, 411, 715, 718, 721).
• Check for connection/breakage of wires (Part #709) and/or soot on the AFR
rod (Part #108).
• Check for connection/breakage of wires (Part #708) and/or burn marks on the
computer board (Part #701).
• Check for connection/breakage of wires (Part #708) and/or burn marks on the
computer board (Part #701).
• 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).
• Inspect the bypass valve (Part #403), for connection/breakage of wires, locked
motor drive due to scale buildup, and/or water leakage.
• Check for connection/breakage of wires (Part #714).
• Refer to the 111 and 121 error codes.
the water heater.
• Check if there is leaking from heat exchanger (Part #401).
• 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.
• Inspect the connections between the water heater and built-in controller.
• Check the power supply of the water heater.
• Check for connection/breakage of wires, dust buildup in the fan motor (Part #103).
• Check for connection/breakage of wires (Part #472, 721).
• 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 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 terminal 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.
55
Page
Owner's Guide
Troubleshooting
Diagnosis
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