Service Manual

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Service Procedure II:
Combustion System Testing and Replacement
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.
Note: On this high input model that uses metal fiber mesh burner a red glow from the burner surface is normal.
N
Gas
Valve/Venturi
Y
Y
N
Y
Y
Y
N
N
N
120 volt potential exposure. Isolate the
appliance and reconfirm power is
disconnected using a multi-meter.
WARNING
N
Continued from previous page.
Y
Y
Refer to control board illustration, is
there 24VAC between brown and
blue wires coming out of the control
harness during the flame establishing
period? Note: Control display must
show “Heating” for operating status.
Check to see brown
and blue wires are
properly connected to
molex connectors on
control harness.
N
Can you hear or feel gas valve
energize?
N
Replace gas valve harness and/or gas valve
(see Gas Valve Replacement Procedure, pg 33).
Clear
obstruction.
Inspect burner
tube (see Burner
Tube Inspection,
pg 31).
Does burner stay lit?
Does burner
operate normally
until thermostat is
satisfied?
Call
Technical
Support.
N
Check flame sensor. Are
there at least 1 to 5 micro
amps (min.) during 1.5
second flame proving
period? Value may be
displayed on the control
display by accessing Service
Mode.
System O.K.
Y
Replace flame sensor (see
Flame Sensor Replacement
Procedure, pg 36).
Inlet
Pressure
Tap
Does burner light smoothly,
without evidence of coughing
or huffing?
Check for obstruction at inlet
of gas valve. Is inlet free of
obstruction?
Replace
control.
Make connections.