A.O. Smith Water Heater 520 Direct Vent Indoor Service Manual page 50

Error Code
Verify fan motor speed
"diagnostics mode" of the 520 models computer board or the 9007603005
621
temperature remote controller.
See the "12-1. How to diagnose the water heater using the 9007603005".
V isual inspection of PCB: connection/breakage of wires and/or burn marks
on the computer board.
Error Code
Abnormal External pump
631
1 Check whether the pump connected to PCB works properly.
Error Code
Water control valve fault
(Flow adjustment function)
651
(Easy-link system only)
1 PCB and flow adjustment valve fault
(Refer to section 10-11 & 10-18)
V isual inspection of Water control valve: connection/breakage of wires,
motor drive locked due to scale buildup, and/or water leakage.
Normal: 13.0 to 16 VDC between (blue-brown)
Normal: ON: 12.5 to 16.0 V / OFF: 0 to 1 V
Normal: 1 V Less than (0˚ position)
V isual inspection PCB: connection/breakage of wires and/or burn marks on
the computer board.
for exhaust of the water heater using the
Malfunction description
Malfunction description
520 Indoor / 520 Outdoor Service Manual
Diagnosis
Turn off the power
Diagnosis
Turn off the power or water supply
Diagnosis
50
CONFIDENTIAL
Ver. 1.00
Checkpoint
Cancellation method
Checkpoint
Cancellation method
Checkpoint
J