Wiring Diagram Checkpoints For Diagnosis - A.O. Smith Water Heater 520 Direct Vent Indoor Service Manual

7. Wiring diagram check points for diagnosis
The table below applies to both the 520 Indoor and 520 Outdoor.
Check-
Part and Description
point
A, A1 100V Power supply
A2 120V Power supply
B1 Heater
B2 Igniter
C Gas valves
C1 Hi-limit switch
C2 Overheat cutoff fuse
D1
Easy-link connectors
D2
520 Indoor / 520 Outdoor Service Manual
Color of wires
White – Black (A)
Brown – Brown (A1)
Black - White
Black - Black
Purple - Purple
Light blue - blue at COM (MV)
Green - blue at COM (SV1)
Orange - blue at COM (SV2)
Red - blue at COM (SV3)
Blue - Blue
Blue - Blue
Red – Red
Blue - Blue
White - White
12
CONFIDENTIAL
Ver. 1.00
Normal range
90 to 110 VAC
108 to 132 VAC
90 to 110 VAC
90 to 110 VAC
78 to 100 VDC (during
operation) / 0.9 to 1.3 kΩ
78 to 100 VDC (during
operation) / 1.3 to 1.9 kΩ
78 to 100 VDC (during
operation) / 1.3 to 1.9 kΩ
78 to 100 VDC (during
operation) / 0.9 to 1.7 kΩ
Less than 1 VDC
and
less than 1.0 Ω
Less than 1 VDC
and
less than 1.0 Ω
15 VDC
(during Easy-link operation)