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