LAARS U.H.E. - Service Manual - Manual (Page 32)

LAARS Heating Systems Page 32
With flame sensor Disconnected
from ignition module, check
continuity to ground.
Is there continuity to ground?
N
Y
Flame Sensor Testing Procedure
Refer to illustration below, is there
a minimum of 1 micro amp during
1.5 second flame proving period?
Y
N
Is flame sensor free
of oxidation?
Clean or replace
flame sensor with emery
cloth. (see page 33)
N
Is ceramic of flame
sensor cracked?
Replace flame sensor.
(see page 33)
Y
N
Flame sensing circuit OK
Y
Refer to ignition module/control board
illustration.(24 volts should maintain beyond the
1.5 second flame proving period.)
Is there 24 volts AC at locations P3(2) & P3(5)?
Y
N
Call for
technical support
Replace flame sensor with
gasket and/or wire lead.
(see page 33)
Remove flame sensor from water heater.
Check continuity from tip of flame sensor
to end of wire lead.
Is there continuity?
N
Y
WARNING
120 volt potential exposure. Use caution
making voltage checks to avoid
personal injury. Flame sensor may be
too hot to handle, take necessary
precautions
32
Flame
sensor
terminal
Volt meter set to
Micro amps setting
(µA)
Meter
probe
Meter
probe
Flame sensor
terminal on
ignition module.