LAARS U.H.E. - Service Manual - Manual (Page 19)

U.H.E Service Manual Page 19
Refer to ignition module illustration below,
is there 24VAC between P3(2) and P3(5) (blue and
brown wires) during the flame establishing period?
(Note: Valve LED must be lit during this check)
Y
Replace
ignition module.
(see page 34)
N
Replace Rectifier harness and/or
gas valve.
(see page 24)
N
Y
Does flame LED on the module
light and stay lit?
Can you hear or feel
gas valve energize?
Does burner light
smoothly, without
evidence of coughing
or huffing?
Y
N
Check for obstruction
at inlet of gas valve.
Is inlet free of
obstruction?
Check flame sensor,
Is there 1 to 5 micro amps
(min.) during 1.5 second
flame proving period?
(see page 32)
N
Y
IGNITION MODULE
Continued from
previous page
N
Call for technical
support
Clear obstruction
Observe burner operation through the sight glass located on the combustion insert mounting flange. Normal burner operation
should ignite smoothly, without evidence of coughing or huffing upon ignition. The burner flame should be a blue flame near the
burner surface in a uniform flame pattern. Occasional yellow or white streaks are normal.
Y
Does burner operate
normaly until thermostat is
satisfied?
N
System OK
Y
Turn VENTURI set screw clockwise until its
bottomed out. Turn screw counter-clockwise 6-½
turns from bottom (see illustration below). Note:
UHE100T399 models do not have a venturi screw.
The gas regulator setting should be 1 - 1 ¼ turns
out from bottom.
Replace flame sensor
(see page 32)
Inspect burner tube, (see page 22)
N
Y
N
WARNING
120 volt potential exposure. Isolate the
appliance and reconfirm power is
disconnected using a multi-meter.
Y
Venturi
adjustment
Inlet gas
pressure tap
UHE100T399
Only
Gas valve
regulator
19