T-M50 / T-M50 ASME Service manual
Ver. 1.05
40
CONFIDENTIAL
Error Code
Malfunction description
Cancellation method
Loss of flame
Turn off the power or water supply
Diagnosis
Checkpoint
1 Check gas supply and pressure (Refer to section 1)
2 Fault of Left and/or Right PCB
[1] No voltage to gas main solenoid valve (MV)
Normal: 78 to 100 VDC between COM (blue) & #3 (light blue)
(during operation)
[2] No voltage to gas solenoid valve (SV
2
)
Normal: 78 to 100 VDC between COM (blue) & #53 (orange)
(during operation)
[3] No voltage to gas proportional valve (VG
0
)
Normal: 1 to 15 VDC between white & red (during operation)
C
H1
3 Gas solenoid fault
[1] Main gas solenoid valve (MV) fault
Normal: 0.9 to 1.3 kΩ between COM (blue) & #3 (light blue)
[2] Gas solenoid valve (SV
2
) fault
Normal: 1.3 to 1.9 kΩ between COM (blue) & #53 (orange)
[3] Gas proportional valve (VG
0
) fault
Normal: 1 to 15 VDC between white & red (during operation)
C
H1
121
Error code is
shown after
three failed
attempts at
ignition
4 Check for soot on the flame rod
[1] Clean the flame rod
[2] Fault of Left and/or Right PCB
During operation: more than 1 μA through the flame rod wire (orange)
I
Error Code
Diagnosis
Checkpoint
7 Inspect flame rod
[1] Check for any soot on the rod.
[2] Check the connection of ground wire; make sure there is firm contact to
the ground of the water heater.
(in this case, the wire is contacted to the manifold surface.)
[3] Fault of Left and/or Right PCB
During operation: more than 1 μA through the flame rod wire (orange)
[4] Flame rod fault (insulated resistance)
During operation: more than 1 μA through the flame rod wire (orange)
I
111
Error code is
shown after
three
failed
attempts
at
ignition
8 Check if hi-limit switch is properly functioning.
