Specifications

TroubleshootingGuide
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17|Page
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4) Iftheerrorcodepersists,replacethethermistor.
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ERRORCODE331:MIXINGTHER MISTOR
1) Checkthatthewireconnectionsaresecureandfreeofburnsorcuts.Themixingthermistoris
embeddedinthewateroutletconnection.
2) Checktheresistancevalue;itshouldbeabout9.0kΩatroomtemperature(about74°F).
3) Cleanthethermistor.
a. Draintheunitofwater.Seep.
23.
b. Removethecomputerboardtoaccessthemixingthermistor.Thecomputeris fixedinplaceby
asinglescrewatthetopoftheboard.
c. Removethescrew,pulloutthesensorprobe.Cleantheprobetoasilverfinish.Donotlosethe
redrubbero‐
ringthatwrapsaroundthissensor.
d. Replaceandtest.
4) Iftheerrorcodepersists,replacethethermistor.
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ERRORCODE341:EXHAUSTTHERMI STOR
1) Checkthatthewireconnectionsaresecureandfreeof
burnsorcuts.Theexhaustthermistorisembeddedat
thetopcenteroftheunitabovetheheatexchanger.
2) Checktheresistanceofthethermistor.Thevalue
shouldbeabout10.75kΩatroomtemperature(about
74°F).
3) Cleanthe
thermistor.
a. Removethescrewholdingthethermistorplate,
thenpulloutthesensorprobe.
b. Cleantheprobetoasilverfinish.Donotlosethe
whitegasketthatsealsthissensor.
c. Replaceandtest.
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4) Iftheerrorcodepersists,replacethethermistor.
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ERRORCODE391:AIR‐FUELRATIORODFAILURE
1) Checkthatthewireconnectionsaresecureandfreeof
burnsorcuts.
2) Checkthattheclearplastictubeconnectingthe
proportionalgasvalvetothecombustionchamber is 
attached.
3) CleantheAFR(p.27).
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Figure12
Figure13
Figure14