Bradford White EF120T4003NA3 Service Manual page 27

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.
Continued from previous page.
Refer to control board illustration. Is
there 24VAC between brown and blue
wires coming out of the control board
harness during the flame establishing
period? Digital display must show
"Heating" for operating status.
Y
Does the gas valve energize?
Y
Does the burner light
smoothly, without evidence of
coughing or huffing?
Y
Does the burner stay lit?
N
Check flame sensor. Are there at
least 1-5 micro amps (min.) during
1.5 second flame proving period?
Value may be displayed on the
control display by accessing
Service Mode.
N
Inspect the burner tube. Replace the
flame sensor (see Flame Sensor
Replacement Procedure, pg 36).
N
Service Procedure II:
Check to see brown
and blue wires are
N
properly connected to
molex connectors on
control board harness.
Y
Replace the
control board.
N
Replace gas valve harness and/or
gas valve (see Gas Valve
Replacement Procedure, pg 29).
Check the air intake and venting
for obstructions or restrictions.
N
Check for obstruction at inlet of
gas valve. Is the inlet free of
obstruction?
Y
Does the burner
operate normally until
thermostat is satisfied?
Y
Y
System O.K.
120 volt potential exposure. Use
caution making voltage checks
N
Make
connections.
N
Clear the
obstruction.
Y
N
Call
Technical
Support.
27
WARNING
to avoid personal injury.
Inlet
Pressure
Tap
Nat. Gas
Valve/Venturi
Inspect the burner
N
tube (see Burner
Tube Inspection,
pg 27).
27