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Standing Pilot Ignition System Troubleshooting Chart
Pilot lit?
Main
burners
light?
Y
Turn control on
gas valve to
PILOT. Depress
red button and
light pilot. Hold
button for at
least one
minute.
Does pilot
light?
N
*Pilot tubing
blocked, kinked
or leaking
*Pilot orifice
blocked
*Gas line not
purged of air
*Pilot improperly
adjusted.
Line pressure
within the range
indicated on
boiler's rating
plate?
Consult gas
supplier.
Does pilot
stay lit?
*Defective thermocouple
*Pilot improperly
adjusted
*Pilot tube blocked, kinked, or
leaking
*Pilot orifice partially plugged
Y
N
N
Y
N
Turn control
on gas valve
to ON.
Y
END
*Defective gas
valve
Y
START
(24 VOLTS PRESENT ACROSS TH AND TR
ON GAS VALVE, BUT MAIN BURNERS DO
NOT LIGHT)
Ensure knob
on gas valve is
set to ON
*Loose
thermocouple
connection at
gas valve.
*Defective
thermocouple.
*Condensation
quenching pilot.
*Low line
pressure.
N
Y
N
Does pilot
stay lit when
red button is
released?
Disconnect
thermocouple from
gas valve. Connect a
volt meter to the
thermocouple. Light
the pilot and hold
down the red button
while reading the
voltage across the
thermocouple.
Is voltage at
least 18mV?
*Loose or defective
thermocouple
connection at gas valve
*Defective gas valve
Y
N
Caution: Read page 34 before
attempting to use this chart
39