Troubleshooting Guide
Maintenance sheet
5M2054-1
B. Error codes
031: Incorrect DIP switch setting
• Check the DIP switch settings on the PCB. Refer to Section E.
101: Warning for the “991” error code
• Check the gas type on the rating plate of the water heater.
• Check to see if there is any blockage in the intake air and/or exhaust. Refer to “Venting
Instructions” in the Installation manual.
• 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. Refer to “Vent termination
clearances” in the Installation manual.
• Check the total vent length. Refer to "Venting instructions" in the Installation manual.
• Check the altitude/elevation of the area where the water heater is installed. Refer to “High-
altitude installation” in Section E. Change the DIP switch settings.
• Check to see if there is grease and/or dirt in the burner (Part #101) and fan motor (Part #103),
especially if the water heater has been installed in a contaminated area.
• Check for dust and lint in the heat exchanger.
• Check the manifold pressure of the water heater. Refer to the rating plate of the water heater.
111: Ignition failure
• Check the gas supply and inlet gas pressure.
• Check to see if the Hi-limit switch (Part #412) is properly functioning.
• Check for disconnections/breakage of wires (Part #413, 708, 709, 711), and/or soot on the flame
rod (Part #108). If the O.H.C.F (Part #413) has a breakage, consult the manufacturer.
• Check for a buzzing spark ignition sound coming from the burner (Part #101) when the water
heater prepares for combustion.
• Listen for the double “clunk” sound coming from the gas valve assembly (Part #102) when the
water heater goes into combustion.
• (Only if sparking and/or clunk sound) Check the voltage on each wire to the gas valve assembly
(Part #102) and/or the igniter assembly (Part #711). Refer to “Appendix A” in Section C.
*No sparking sound >>>>> Refer to #1 in “Appendix A,” Section C.
*No clunking sound >>>>> Refer to #2 in “Appendix A,” Section C.
• Check for leaking from the heat exchanger (Part #401).
• Check for dust and lint in the nozzles of the manifold (Part #102).
• Check the current of the flame rod (Part #108). Refer to #3 in “Appendix A,” Section C.
121: Loss of flame
• Check the gas supply and inlet gas pressure.
• Check to see if the Hi-limit switch (Part #412) is properly functioning.
• Check for disconnections/breakage of wires (Part #413, 708, 709, 711), burn marks on the PCB
(Part #701), and/or soot on the flame rod (Part #108). If the O.H.C.F (Part #413) has a breakage,
Consult the manufacturer.
• Check for leaks from the heat exchanger (Part #401).
• Check for dust and lint in the nozzles of the manifold (Part #102).
• Check the current of the flame rod (Part #108). Refer to #3 in “Appendix A,” Section C.
311,321,331,341,351: Disconnected/short-circuited thermistor
• Check for disconnections/breakage of wires and/or debris on the thermistors (Part #407, 408, 411, 718, 731).
• Check the thermistor resistance. Refer to “Appendix D” in Section C.
391: Air-fuel ratio rod failure
• Check for disconnections/breakage of wires (Part #709) and/or soot on the flame rod (Part #108).
441: Flow sensor failure
• Check for disconnections/breakage of wires and/or debris on the flow sensor impeller (Part #402).
• Check the filter on the return connection to see if it is clogged. (Part #406)
• Check to see if the water in the pump pipe system has frozen.
510,551: Abnormal main gas solenoid valve and gas solenoid valve
• Check for connection/breakage of wires (Part #708) and/or burn marks on the computer board (Part #701).
• Reset the power supply of the water heater.
• Check the voltage of each valve on the gas valve assembly (Part #102). Refer to “Appendix C” in Section C.
611: Fan motor fault
• Check for disconnections/breakage of wires, dust buildup in the fan motor (Part #103) and/or
burn marks on the PCB (Part #701).
• Check for frozen/corrosion of connectors of the fan motor (Part #103).
• Check the voltage between the blue wire and each wire of the fan motor (Part #103). Refer to
“Appendix B” in Section C.
631: Pump fault
• Check for disconnections/breakage of wires in the pump (Part #726).
• Check to see if the water in the pump has frozen (Part #726).
651: Flow adjustment valve fault (Only Easy-Link System)
• Inspect the flow adjustment valve (Part #402) for disconnected or broken wires. Also chcek for a
locked motor drive due to scale buildup, and/or water leakage.
• Check the voltage between the black and red wires. Refer to “Appendix F” in Section C.
661: Bypass valve fault
• Inspect the bypass valve (Part #403) for disconnected or broken wires. Also chcek for a locked
motor drive due to scale buildup, and/or water leakage.
• Check the voltage between the brown and red wires. Refer to “Appendix F” in Section C.
701: PCB fault
• Check for disconnections/breakage of wires (Part #714), and check the resistance between the
white and red wires. Refer to “Appendix A” in Section C.
• Check the outlet thermistor (Part #408) for proper readings as it may need to be cleaned.
711: Gas solenoid valve drive circuit failure
• Refer to the “111” and “121” error codes in this section.
721: False flame detection
• Clean the flame rod (Part #108).
• Check for leaks from the heat exchanger (Part #401).
741: Miscommunication between water heater and remote controller
• Check the model type of the remote controller. Model No. 100276687 (TM-RE43) is the correct one.
• Inspect the connections between the water heater and remote controller. Refer to
“TEMPERATURE REMOTE CONTROLLER” in the Installation manual.
• Check the power supply of the water heater.
• If this error code appears only on the green LED on the PCB (Part #701), check the voltage on the
remote controller terminal on the PCB. Refer to “Appendix E” in Section C.
• If this error code appears only on the remote controller, replace the PCB (Part #701).
• If this error code appears on both the PCB (Part #701) and the remote controller, replace the remote controller.
751: Miscommunication between water heater and built-in controller
• Check the power supply of the water heater.
• If this error code appears only on the green LED in the PCB (Part #701), check the voltage on the
built-in controller terminal on the PCB. Refer to “Appendix E” in Section C.
• If this error code appears only on the built-in controller, replace the PCB (Part #701).
• If this error code appears on both the PCB (Part #701) and the built-in controller, replace the
temperature controller.
761: Miscommunication between Parent unit and Child units in Easy-Link System
• Make sure that the connections between the parent unit and the child units are correct. Refer
to the “Easy-Link System” section in the Installation manual.
941: Abnormal exhaust temperature (Indoor model)
• Check for disconnections/breakage of wires, dust buildup in the fan motor (Part #103) and/or
burn marks on the PCB (Part #701).
• Check the resistance of the exhaust thermistor. Refer to "Appendix D" in Section C.
• Check to see if the inlet and return water temperature is higher than 140°F (60°C) in the recircu-
lation system.
991: Imperfect combustion
• Refer to the “101” error code in this section.
C. Wiring diagram
and checkpoints
Appendix A (Error code 111)
Check the following points during ignition stage.
#1. Refer to checkpoint “B” on the wiring diagram above.
Check the voltage between purple wires. (Normal: 108 to 132 VAC)
Is the voltage within normal range?
Yes >>Replace the igniter assembly (Part #711).
No >>Go to Error code in Section B.
#2. Refer to checkpoints “C” and “H1” on the wiring diagram above.
Check the voltages below:
C: Between the blue and light blue wires (#3). (Normal: 93 to 120 VDC)
C: Between the blue and orange wires (#53). (Normal: 93 to 120 VDC)
H1: Between the white and red wires. (Normal: 1 to 15 VDC)
Are these voltage within normal range?
Yes >>Replace the gas valve assembly (Part #102).
No >>Replace the PCB (Part #701).
#3. Check the current through the orange flame rod wire (Part #709).
(Normal: more than 5 μA)
Is the current normal when there is a flame?
Yes >>Replace the PCB (Part #701).
No >>Replace the flame rod (Part #108).
Appendix B (Error code 611)
Refer to checkpoint “G” in the diagram above and check the voltage
• Between the red and blue wires. (Normal: 132 to 192 VDC)
• Between the yellow and blue wires. (Normal: 13 to 17 VDC)
• Between the orange and blue wires. (Normal: 2.0 to 6.5 VDC)
Are all of the voltages within normal range?
Yes >>Replace the fan motor (Part #103).
No >>Replace the PCB (Part #701).
Appendix C (Error code 510 and 551)
Refer to checkpoint “C” in the diagram above and check the voltage on each
valve on the gas valve assembly.
• Between the blue and light blue wires (#3). (Normal: 93 to 120 VDC)
• Between the blue and green wires (#9). (Normal: 93 to 120 VDC)
• Between the blue and orange wires (#53). (Normal: 93 to 120 VDC)
• Between the blue and red wires (#73). (Normal: 93 to 120 VDC)
Are all of the voltages within normal range?
Yes >>Replace the gas valve assembly (Part #102).
No >>Replace the PCB (Part #701).
Appendix D (Error code 311, 321, 331, 341, 351 and 941)
Check the resistance between the black wires.
• Outlet thermistor “E1” (Find the marking of No. 113 on the connector.)
• Inlet thermistor “E2” (Find the marking of No. 42 on the connector.)
• Heat exchanger thermistor “E3” (Find the marking of No. 12 on the connector.)
• Return thermistor “E4” (Find the marking of No. 14 on the connector.)
Temperature
°F 50 59 68 77 86 95
°C 10 15 20 25 30 35
Resistance kΩ 15.4 12.6 10.3 8.5 7.0 5.9
Appendix D (Error code 311, 321, 331, 341, 351 and 941)
Check the resistance between the white wires.
• Exhaust thermistor “K1”
Temperature
°F 50 59 68 77 86 95
°C 10 15 20 25 30 35
Resistance kΩ 19.5 15.9 13.0 10.7 8.9 7.4
Are all of the checkpoints normal?
Yes >> Replace the PCB. (Part #701)
No >> Replace the defective thermistor.
(Part #407/408/411/718/731)
Appendix E (Error code 741 and 751)
Error code 741: Refer to checkpoint “F” on the wiring diagram.
Error code 751: Refer to checkpoint “L” on the wiring diagram.
Check the voltage between the black and white wires.
(Normal: 11 to 25 VDC)
Is the voltage within normal range?
Yes >>Replace the built-in/remote controller.
(Part #722/724)
No >>Replace the PCB. (Part #701)
If the error code is displayed on the built-in controller and/or the remote controller, refer to Section B.
<< It takes a long time to get hot water at the fixtures >>
• Check to see if a recirculation timer is active. If not, it will take time for the hot water to get
from the heater to the fixture.
• Check the recirculation pump for proper flow.
• The inlet filters on the return and inlet connections may need to be cleaned.
<< The water is not hot enough or turns cold and stays cold >>
• Compare the flow and temperature. Refer to “Output temperature chart” in the Installation manual.
• Check cross plumbing between cold water lines and hot water lines.
• Check if the gas supply valve is fully open, the gas line is sized properly, and the gas supply
pressure is within specified limits. Refer to “Gas supply and gas pipe sizing” in the Installation manual.
• Check the set temperature on the built-in controller/remote controller. If necessary, change
the set temperature with the controller or the DIP switch setting. Refer to Section E.
• Refer to “Water circuit” in this section.
• Is the Easy-Link System set up correctly?
<<The water is too hot>>
• Check the set temperature and lower it, if necessary.
<<The hot water is not available when a fixture is opened>>
• Refer to “Power supply circuit” and “Water circuit” in this section.
• Is the Easy-Link System set up correctly?
<<Fluctuation in hot water temperature>>
• Check the filters on the cold water inlet and return connection to see if they are clogged. (Part #406)
• Check to see if the gas valve is fully open, that the gas line is sized properly, and that the
supply gas pressure is within specified limits.
• Check for a cross connection between cold water lines and hot water lines.
• Refer to “Water circuit” in this section.
• Is the Easy-Link System set up correctly?
A. Troubleshooting
<<Unit does not ignite when water goes through the water heater>>
• Refer to “Power supply circuit” and “Water circuit” in this section.
• Check to see if the filters on the cold water inlet and return connection are clogged. (Part #406)
• Check to see if the inlet temperature is too high.
<<The fan motor is still spinning after operation has stopped>>
• This is normal. After operation has stopped, the fan motor keeps running for 15 to 70 seconds
so that it can re-ignite quickly, as well as to purge all of the exhaust gas out of the flue.
<<Abnormal sounds from water heater>>
• Abnormal sounds from the water heater are caused by limited air supply or an incorrect installation.
The water heater needs more combustion air. Refer to the “101” error code in the section B.
<<Power supply circuit>>
1. Check the power supply, and make sure that the water heater has 120 VAC.
2. Is the power switch inside the water heater turned on? (Part #706)
3. Press the “ON/OFF” button on the built-in/remote controller, and make sure that the STAND BY
LED is lit. Run the water heater.
4. Check to see if the green LED on the PCB (Part #701) is lit. If so, the power supply circuit for the water
heater is under normal condition; refer to “Water circuit” in this section.
5. Check the fuse on the surge box (Part #703), and if it has a brown spot, replace it.
6. If the green LED on the PCB (Part #701) is not lit, some electrical parts may be broken. Consult
the manufacturer.
<<Water circuit>>
1. Press the “ON/OFF” button of the built-in/remote controller, and make sure that the STAND BY LED is lit.
2. Open all hot water faucets, and make sure that there is enough water flow. This water heater
needs at least 0.5 GPM water flow (at the default set temperature) to operate.
3. Check for reverse connections and cross connections.
4. Check to see if the filters on the cold water inlet and return connection are clogged or if there is
sediment bult up in the filters. (Part #406)
5. Check for debris or obstructions in the fixtures.
6. Check to see if the water ways in the water heater are frozen. If so, thaw them. Refer to the
installation manual to protect your water heater from freezing.
7. Make sure that the inlet water pressure is higher than 40 psi. If it is lower than 40 psi, increase the pressure.
8. Check the wiring connections and for breakage of wires (Part #402).
9. Check to see if the motor drive of the flow adjustment valve (Part #402) is locked due to scale
buildup. Also check for water leakage. If these symptoms are present, consult the manufacturer.
540P
Appendix F (Error code 651 and 661)
Error code 651 : Refer to checkpoint “J” on the wiring diagram.
Check the voltage between the black and red wires.
(Normal: 7 to 16 VDC)
Error code 661 : Refer to checkpoint “J1” on the wiring diagram.
Check the voltage between the brown and red wires.
(Normal: 3 to 11 VDC)
Is the voltage within normal range?
Yes >>Error code 651:
Replace the flow adjustment valve.
(Part #402).
>>Error code 661:
Replace the bypass valve (Part #403).
No >> Replace the PCB (Part #701).
Appendix G (Error code 631)
Refer to checkpoint “M” in the diagram above and check the voltage
below.
• Between the blue and red wires. (Normal: 140 to 200 VDC)
• Between the blue and yellow wires. (Normal: 14 to 16 VDC)
• Between the blue and orange wires. (Normal: 1 to 6.5 VDC)
Are all of the voltages within normal range?
Yes >>Replace the pump assembly (Part #726).
No >>Replace the PCB (Part #701).
W: WHITE
R: RED
BK: BLACK
P: PURPLE
LB: LIGHT BLUE
BL: BLUE
G: GREEN
Y: YELLOW
O: ORANGE BR: BROWN
Return thermistor
Heat exchanger
thermistor
Inlet thermistor
Outlet thermistor
Exhaust thermistor
Hi-limit switch
for exhaust
Parent
540P Indoor Only
540P Indoor Only
540P Indoor Only
540P Outdoor Only
Green LED
DIP switches
Flame rod
Ground
Air-fuel rao rod
Y
G
O
IG
Igniter rod
P
P
120 VAC
G
Ground
W
BK
Surge
box
W
BK
G
W
BK
Ground
SW
W
BK
3
9
53
73
MV
SV3
SV2
SV1
LB
G
O
R
BL
O.H.C.F
BL
BL
W
W
Hi-
limit
BL
BL
W
Y
BL
O
R
FM
Bypass
Valve
R
Y
W
BL
BR
65432
1
87
ON
65432
1
ON
432
1
ON
Increase buon
Decrease buon
MAX. buon
MIN. buon
BK
BK
BK
BK
BK
BK
BK
BK
W
Y
BL
O
R
Pump
W
BL
Remote
controller
Built-in
controller
W
BL
R
BK
Thermostat
Heater
Heater
Heater
Heater
Heater
Heater
Heater
Heater
Y
Y
Y
Y
Y
Y
BK
W
BK
W
W
W
W
Flow
Adjust
Valve
R
BK
BK
W
R
Flow
Sensor
Gas
Propor-
onal
Valve
W
R
C
A1
A2
B1
G
A
B
C2
C1
H2
I
F
J
E1
E4
E2
E3
H1
K1K2
J1
D
M
L
Error codes 341, 751, and 941 apply to Indoor model only.