Service Manual

77
Service Procedure VI:
Flame Sensor Testing and Replacement
Flame Sensor Testing Procedure
WARNING
120 volt potential exposure. Use caution making
voltage checks to avoid personal injury.
Refer to the illustration
below. Is there a minimum
of 1 µA during 1.5 second
flame proving period?
Refer to the ignition
module/control board illustration.
24 volts should maintain beyond
the 1.5 second flame proving
period. Is there 24 VAC between
P5(5) and P5(8)?
Flame sensing
circuit O.K.
With flame sensor
disconnected from ignition
module, check continuity to
ground. Is there continuity
to ground?
Remove the flame sensor
from the water heater.
Check continuity from the
tip of the flame sensor to
the end of the wire lead.
Is there continuity?
Replace the flame
sensor with the
gasket and/or wire
lead (see Flame
Sensor
Replacement
Procedure, pg 78).
Call Technical Support.
Is the flame sensor free of
oxidation?
Is the ceramic of the
flame sensor cracked?
Clean or replace the
flame sensor (see Flame
Sensor Replacement
Procedure, pg 78).
Replace the flame
sensor (see Flame
Sensor Replacement
Procedure, pg 78).
Call Technical Support.
Multimeter set
to microamp
(µA) setting
Flame sense
terminal
Flame sense
rod
N
N
N
N
N
N
Y
Y
Y
Y
Y
Y
77