Afr Rod - A.O. Smith T-D2-OS Service Manual

10-6. AFR rod

Unit 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 AFR rod is assembled with the flame rod.
Detecting elements (AFR and flame rods)
Leads to computer board
#108 Takagi Part #
-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 will not initiate the ignition process. The "721" error
code will display.
2. 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(8) - AFR rod
(Between AFR rod and the
computer board)
T-D2-IN / T-D2-OS Service Manual
EKK0E
391
More than DC 0.5 μA
22
CONFIDENTIAL
Ver. 1.00
Checkpoint
991
(During operation)
I