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240 (T-H3J), 340 (T-H3S) and 540 (T-H3) models Service Manial
Ver. 1.00
CONFIDENTIAL
10-6. AFR rod
Part #
• 319143-517 (EK193)
Unit Part#
#108
Function
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.
Failure events
1. Unable to detect flames when flames actually do occur.
2. Detecting a false flame when no flames actually occur.
Effects on the water heater
if AFR rod fails
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.
Error codes when
the AFR rod fails
101 391 991
Diagnostic
1. Visual inspection: connection/braking of wires, soot on it.
2. Check voltages: proper range of values are shown below.
Color / Number of wires
Yellow - AFR rod
(Between the AFR rod and
the computer board)
(During operation)
More than DC 1 μA
Check
point
I
The flame rod is assembled with the AFR rod.
3/4" (19.5 mm)
1" (27 mm)
1/2" (12 mm)
2-1/8" (54 mm)
Lead to computer board
Detecting elements
(AFR and flame rods)
Black mark