A.O. Smith 310 - ERROR CODE 121 FLAME LOSS

TroubleshootingGuide
14|Page
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gasmeter.
b. Forpropaneunits,colderperiodsofthedayresultinacoldregulatorandmaycausethis
problem.
3) Verifythatthegassupplypressureiswithinspecificationswhentheheaterisinstandbyandwhen
theheaterisrunning.
4) Checkthattheclearplastictubeconnecting
theproportionalgasvalvetothecombustionchamber
isattached.
5) Theoverheatcutofffuse(OHCF)mayhavebeencompromised.Forproceduresonhowtocheck
whethertheOHCFisintact,refertop.24.IftheOHCFhasbeencompromised,contactthe
TechnicalServiceDepartmentforfurtherassistance.
6)
Ifflamecomesonforonly1‐2secondsbeforegoingout,cleantheflamesensor(p.25).
7) Checktheigniterforaspark.Thesparkmaybeviewedthroughthesightglasslocatednexttothe
igniterandflamesensor.

a. Astrongbluesparkwillremainsteadyandinplace,whileaweaksparkwilljumparound.
b. Ifnosparkoraweaksparkisobserved,checktheigniterwireconnectionsandmakesurethese
aresecure.Ifthesearesecure,areplacementigniterwillberequired.
8)
Checkforblockagesintheventing,suchasbirdnests,animals,ortrash.
a. PCBoardfaultorGasSolenoidfault.ContacttheTechnicalServiceDepartment.
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ERRORCODE121[510(T‐D2)],THREEFLASHES/12[110(T‐KJR2),310(T‐K4)]
FLAMELOSS
Thiserrorcodeappearsiftheflamesdisappear whiletheunitisstillsupposedtobeinoperation. 
1) Verifythatthehi‐limitswitchisnottripped.Turnthepowerofftotheunit.Pushthewhitebutton
in.Theswitchwillresetwhenyouhearandfeelthebutton
click.Turnthepowerbackonandtest
theheater.Iftheunitfireson,thecauseofthehi‐limittripmustbedetermined.Pleasecontactthe
TechnicalServiceDepartmentforfurthertechnicalsupport.
2) Checkthegassupply.Verifythatsufficientgasisbeingsuppliedtotheheater
andthegaslineis
clearedofdebris.
a. Itispossiblethereisafaultypressureregulatoratthegasmeter.
b. Forpropaneunits,colderperiodsofthedayresultinacoldregulatorandmaycausethis
problem.
3) Verifythatthegassupplypressureiswithin
specifications
whentheheaterisinstandbyandwhen
theheaterisrunning.
4) Checkthattheclearplastictubeconnectingthe
proportionalgasvalvetothecombustionchamber is 
attached.
5) Iftheflamecomesonfor1‐2secondsbutthengoes
out,cleantheflamesensor(p.25).
6) Theoverheatcutofffusemayhavebeen
compromised.Forproceduresonhowtocheck
whethertheOHCFisintact,refertop.24.Ifithas,
contacttheTechnicalServiceDepartmentforfurther
assistance.
7) Checkforblockagesinventing,suchasbirdnests,animals,ortrash.
8) PCBoard
faultorGasSolenoidfault.
a. Ifoneoftheseissuspectedtobetheproblem,contacttheTechnicalServiceDepartment.
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Figure7