A.O. Smith Water Heater 520 Direct Vent Indoor Service Manual page 43

Natural of
Fault
4 Fault of PCB in the water heater
Fluctuation
[1] No voltage to gas solenoid valve (SV
of hot water
Normal: 78 to 100 VDC between COM (blue) & #9 (green)
temperature
(during operation)
[2] No voltage to gas solenoid valve (SV
Normal: 78 to 100 VDC between COM (blue) & #73 (red)
(during operation)
5 Gas solenoid valve (SV
[1] Disconnected wiring to gas solenoid valve (SV
Normal: 1.3 to 1.9 kΩ between COM (blue) & #9 (green)
[2] Disconnected wiring to gas solenoid valve (SV
Normal: 0.9 to 1.7 kΩ between COM (blue) & #73 (red)
6 Fault of PCB in the water heater
No voltage to water control valve
Normal: 13.0 to 16.0 VDC between (blue-brown)
Normal: ON 12.5 to 16.0 V / OFF 0 to 1 V between (orange-brown)
Normal: 1 VDC less (0˚ position) between (red-brown)
7 Fault of Water control valve
Normal: 0.09 to 0.2 kΩ between (red-black)
Error Code
Incorrect dipswitch setting fault
031
Check the dipswitch settings on PCB
Error Code
Warning for the "991" error code
(Refer to section 12-3)
1 Check the gas type of the water heater.
101
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.
) fault
1
Malfunction description
Malfunction description
520 Indoor / 520 Outdoor Service Manual
Diagnosis
).
1
).
3
)
1
)
3
Turn off the power or water supply
Diagnosis
On the PCB, press the INC and DEC
buttons simultaneously for 3 sec. Then
turn the power off.
Diagnosis
43
CONFIDENTIAL
Ver. 1.00
Checkpoint
Cancellation method
Checkpoint
Cancellation method
Checkpoint
C
C
J
J