A.O. Smith T-M50 ASME Service Manual page 39

Error Code
8 Check if there is dust and lint in burner and heat exchanger, when the water
heater has been installed in laundry room.
101
9 Check if there is grease and dirt in burner and fan motor, when the water
heater has been installed in restaurant.
10 Check the manifold pressure in the water heater.
Error Code
Ignition failure
111
1 Check gas supply and inlet gas pressure (Refer to section 1)
2 Check the igniter (Refer to section 10-18)
V isual inspection: connection/breakage of wires and/or observed weak
Error code is
spark.
[1] Cracks/soot on igniter rod
shown after
[2] Improper gap between burner & igniter rod
three failed
Normal gap: 0.16" (4mm)
attempts at
[3] Fault of Left and/or Right PCB
ignition Normal: 90 to 110 VAC at #7 (purple-purple) (during ignition)
3 Fault of Left and/or Right PCB
[1] No voltage to main gas solenoid valve (MV)
Normal: 78 to 100 VDC between COM (blue) & #3 (light blue)
[2] No voltage to gas solenoid valve (SV
Normal: 78 to 100 VDC between COM (blue) & #53 (orange)
[3] No voltage to gas proportional valve (VG
Normal: 1 to 15 VDC between white & red
4 Gas solenoid valve 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
Normal: 1.3 to 1.9 kΩ between COM (blue) & #53 (orange)
[3] Gas proportional valve (VG
Normal: 1 to 15 VDC between white & red
5 Disconnected/damaged O.H.C.F.
V isual inspection: connection/breakage of wires.
Normal: 1 Ω or less between blue & blue
6 Disconnected/damaged hi-limit switch. (Refer to section 10-11)
V isual inspection: connection/breakage of wires.
Normal: 1 Ω or less between blue & blue
Malfunction description
) fault
2
) fault
0
T-M50 / T-M50 ASME Service manual
Diagnosis
Turn off the power or water supply
Diagnosis
)
2
)
0
(Refer to section 10-12)
39
CONFIDENTIAL
Ver. 1.05
Checkpoint
Cancellation method
Checkpoint
B
C
H1
C
H1
C2
C1