Flame Rod - A.O. Smith Water Heater 520 Direct Vent Indoor Service Manual

10-6. Flame rod

Unit Part #
Function
Failure events
Effects on the water
heater if flame rod fails
Error codes when the
flame rod fails
Diagnostic
Color/Number of wires
The flame rod is assembled with the AFR rod.
Leads to computer board
#106 AOS Part #
To detect flames while the water heater is in operation.
1. Unable to detect flames when flames actually do occur
2. Detecting a false flame when no flames actually occur
1. The water heater stops operating. The "111" and/or "121" error code(s)
will display.
2. The water heater will not initiate the ignition process. The "721" error
code will display.
111
1. Visual inspection: connection / breakage of wires or soot buildup on rod.
2. Check Amperes: proper range of values shown below.
Orange(17) - Flame rod
(Between flame rod and the
computer board)
Detecting elements of the flame rod
520 Indoor / 520 Outdoor Service Manual
319143-035
121
More than DC 1 μA
23
CONFIDENTIAL
Ver. 1.00
Checkpoint
721
(During operation)
I