A.O. Smith T-D2-OS - Page 38

T-D2-IN / T-D2-OS Service Manual
Ver. 1.00
38
CONFIDENTIAL
Natural of
Fault
Diagnosis
Checkpoint
・ Fluctuation
of hot water
temperature
4 Fault of PCB in the water heater
[1] No voltage to gas solenoid valve (SV
1
).
Normal: 78 to 100 VDC between COM (blue) & #9 (green)
 (during operation)
[2] No voltage to gas solenoid valve (SV
3
).
Normal: 78 to 100 VDC between COM (blue) & #73 (red)
(during operation)
C
5 Gas solenoid valve (SV
1
) fault
[1] Disconnected wiring to gas solenoid valve (SV
1
)
Normal: 1.3 to 1.9 kΩ between COM (blue) & #9 (green)
[2] Disconnected wiring to gas solenoid valve (SV
3
)
Normal: 0.9 to 1.7 kΩ between COM (blue) & #73 (red)
C
6 Fault of PCB in the water heater
No voltage flow adjustment valve
Normal: 7
to
16
V
DC
between (red
-
black)
J
7 Flow adjustment valve fault
Normal: 0.09 to 0.2 kΩ between (red-black)
J
Error Code
Malfunction description Cancellation method
031
Incorrect dipswitch setting fault Turn off the power or water supply
Diagnosis Checkpoint
Check the dipswitch settings on PCB
Error Code
Malfunction description Cancellation method
101
Warning for the “991” error code
(Refer to section 12-3)
On the PCB, press the INC and DEC
buttons simultaneously for 3 sec. Then
turn the power off.
Diagnosis Checkpoint
1 Check the gas type of the water heater.
2 Check how long the water heater has been installed and in use.
3 Check the installation location.
4 Check the altitude/elevation of area of where the water heater installed.
5 Check the vent length.
6 Check if there is any blockage in the intake air and/or exhaust.
7 Check if there is dust and lint in burner and heat exchanger, when the water
heater has been installed in laundry room.