A.O. Smith T-M50 ASME Service Manual page 45

Error Code
1 Fault of Left and/or Right PCB
[1] Fault of preparation for the mixing thermistor
701
operation.
[2] Fault of driving circuit for Gas Proportional
Valve(VG
1 Check the PCB and/or gas proportional valve
(Refer to section 10-4, 10-14 and 10-15)
V isual inspection PCB: connection/breakage of wires and/or burn marks on
the computer board.
V isual inspection gas proportional valve: connection/breakage of wires of
the gas proportional valve.
Normal: 20 to 40 Ω between (white) & (red)
Error Code
False flame detection
721
1 False flame detection (5 sec.)
Flame rod (Insulated resistance) fault
Error Code
741
Miscommunication between water heater and
remote controller
1 Temperature remote controller or central computer board fault.
2 Check for signs of power surges.
Malfunction description
)
0
Malfunction description
Malfunction description
T-M50 / T-M50 ASME Service manual
Turn off the power or water supply
Diagnosis
Turn off the power or water supply
Diagnosis
Restoring
between the water heater and the
Remote controller. When the computer
detects proper connections between the
water heater and the Remote controller,
"741" error code will cease to display.
Diagnosis
45
CONFIDENTIAL
Ver. 1.05
Cancellation method
Checkpoint
Cancellation method
Checkpoint
Cancellation method
proper cable connections
Checkpoint
H1
I