Siemens LMV52.440B1 - O 2 Sensor Reading Grossly High or Low; O 2 Sensor Reads but Responds very Slowly

TechnicalInstructions  LMVSeries
DocumentNo.LV5‐1000
Section7 Page14 SCCInc.
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O2SensorReadingGrosslyHighorLow
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IftheO
2
readingsfromtheO
2
sensoraregrosslyhighorlow,checkthefollowing:
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1. Themilli‐voltsignalsfromtheQGO20tothePLL52couldhaveinterference.Ensurethatthe
highandlowvoltagewiresthatrunfromtheQGO20tothePLL52areinaseparateconduit.
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2. TheQGO20sensorreads%O
2
wet.Mostcombustionanalyzersread%O
2
dry,sotheO
2

numbershownontheAZL52istypicallyatleast1%O
2
lowerthanthecombustionanalyzer.
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3. TheQGO20sensormaybemountedincorrectly,andthesensorisnotpickingupa
representativereadingofthe%O
2
inthestack.
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O2SensorReadsButRespondsVerySlowly

Ifthe%O
2
beingdisplayedisrespondingslowlytocombustionchanges,checkthefollowing:
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1. EnsurethattheQGO20sensorisclean.Thiscanbedonebyshuttingoffthe powertothe
LMV52,andremovingtheQGO20fromthestack.Becarefulasthesensorislikelytobevery
hot.AftertheQGO20isremovedfromthestack,letitcoolforatleastanhour.
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 Afterthesensorhascooled,itcanbeblownoutusinglowpressurecompressedair(less
than15PSIG)throughthetopofthesensorandoutthefront.Ifthisisdonewhenthe
QGO20sensorishot,theceramicsinsidethesensorwillmostlikelybecrackedandthe
sensorwillneedtobereplaced.
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2. ChecktheorientationoftheQGO20sensorandtheAGO20collector.Theonenotchonthe
AGO20collector’sflangeshouldbebetweenthetwonotchesontheQGO20sensor’sflange.
Also,ensurethatthebevelofthecollectorispointedintotheflowofthestackgas.
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3. Checktheinternalresistance
oftheQGO20sensorusingthefollowingmenupath:
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 Params&Display>O2Module>ProcessData>QGOResistance
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 Thisvalueincreasesasthesensorages.Astheinternalresistanceincreases,theresponse
timeofthesensoralsoincreases.
Anewsensorhas0Ohms,whilethemaximumresistance
is150Ohms,indicatingreplacementofthesensorisnecessary.
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