Afr Rod - A.O. Smith T-H3J-DV Service Manual

10-6. AFR rod

Part #
Function
Failure events
Effects on the water heater
if AFR rod fails
Error codes when
the AFR rod fails
Diagnostic
Color / Number of wires
The flame rod is assembled with the AFR rod.
Lead to computer board
240 (T-H3J), 340 (T-H3S) and 540 (T-H3) models Service Manial
• 319143-517 (EK193)
Checks flame conditions during combustion.
When AFR rod detects unexpected flame conditions, the computer of the
water heater makes adjustments in the fan motor speed to compensate.
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.
3. The fan motor speed cannot be modulated properly under abnormal
flame conditions, which can result in excessive CO emission.
101
1. Visual inspection: connection/braking of wires, soot on it.
2. Check voltages: proper range of values are shown below.
Yellow - AFR rod
(Between the AFR rod and
the computer board)
Detecting elements
(AFR and flame rods)
Black mark
27
Page
CONFIDENTIAL
Unit Part#
391
(During operation) Check
More than DC 1 μA point
3/4" (19.5 mm)
Ver. 1.00
#108
991
I