General Troubleshooting Chart - McFarlane Aviation Products

Troubleshooting ChartSYMPTON PROBABLE CAUSE SOLUTIONNO INDICATION OFMETERLOW READINGHIGH READINGShorted or open lead and probecircuitPossible probe, meter, or leadincompatibilityMeter out of calibrationFriction in movementBad or dirty and corrodedpotentiometerMeter out of calibrationThermocouple wire touchingtogether other than probe tip,causing secondary thermocouplejunction.EGT Type K probe on Type EsystemHigh resistance in systemBad or dirty potentiometer that iscorroded.Meter out of calibrationRepair lead, replace probe, and recheck lead andprobe loop resistance. Do system check with Alcal2000 system tester.Check that meter, lead, and thermocouple are thesame type, by checking the color codes and partnumbers.Recalibrate in flight if relative reading or for truetemperature use the Alcal 2000 tester.Worn jewels, call Alcor for meter repair orreplacementAttempt to move the pot back and forth to self-cleanand recalibrate. *See NoteRecalibrate in flight for relative reading or for truetemperature reading use the Alcal 2000 testerInspect the insulation and connection of thethermocouple and lead. Perform loop resistancecheck of thermocouple and lead. If okay, complete aheat check on probe. Correct the connection orreplace component.Install Type K probeCheck probe and lead loop resistance. Replace if outof toleranceAttempt to move pot back and forth to self-clean andrecalibrate.* See NoteRecalibrate in flight for relative reading EGT or fortrue temperature reading use the Alcal 2000 tester.ERRATIC READINGEGT Type E Probe on Type KsystemAn open thermocouple, RTD, orconnection on some types ofamplified systems.CHT Engine cooling baffling isleakingCHT Gasket Thermocouple isusedLead receiving bus currentthrough induction. (Test by turningoff Master Switch andalternator/generator.Bad potentiometer or friction inmovement.Internally broken probe leadwires, causing intermittentconnection.Install Type K probeTest and if defective replace componentRepair and replace bafflingSpark plug is higher temperature than cylinderRe-route lead away from current carrying wire.Call ALCOR to repair or replace.Check probe resistance by wiggling wire and replaceif out of tolerance or fluctuates.

INDICATORCHANGES WHENTAPPEDNO INDICATION ATRUN-UPINDICATOR WORKSON BENCH, BUT NOTIN FLIGHTLead chafed and groundingintermittentlyFriction in movement or old stylepot needs exercising or replacing.EGT Indicator begins at 1200°F.Note: All engines may not reach1200°F at run-up power whileleaned.CHT needs adequate time forwarm up, meter out of calibration,or meter or probe inoperative.Check probe and lead resistance.If okay, there may be excessiveresistance or friction in meter orpot in poor condition.Insulate from airframeCall ALCOR to repair or replaceCheck operation while in flightTest systemCall ALCOR to repair or replace