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Troubleshooting Aircraft Charging Systems ( Alternators/Reciprocating Engines)

Troubleshooting Aircraft Charging Systems ( Alternators/Reciprocating Engines). by Herb Spenner. Troubleshooting Steps. Setup Connections Electrical Components Finish Up. Setup. Avionic must be turned off Protects them from damage Master switch – On – when checking voltage

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Troubleshooting Aircraft Charging Systems ( Alternators/Reciprocating Engines)

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  1. TroubleshootingAircraft Charging Systems(Alternators/Reciprocating Engines) by Herb Spenner

  2. Troubleshooting Steps • Setup • Connections • Electrical Components • Finish Up

  3. Setup • Avionic must be turned off • Protects them from damage • Master switch – On – when checking voltage • Master switch – Off – when checking resistance • Select multi-meter range before measuring • Secure item before running engine

  4. Connections • Check circuit breakers • If tripped, find out why • Remind customer of Special Airworthiness Information Bulletin (SIAB) CE 11-10 • Electrical: Fire Hazard in Resetting Circuit Breakers • Check grounding straps • Refer to AC 43.13-1B – 11-188 • Use Low Ohm Meter (LMO) to check connections • Standard multi-meter not sensitive enough • See Practical Low Resistance Measurement – Bob Neckolls

  5. Connections • Check all mechanical connections are tight • Cleanup all corrosion • Check for damaged insulation • Recommend customer replace old aluminum battery cable • Better cold starts • Save money through longer component life • Check alternator belt • Insure alternator bearings work smoothly

  6. Typical Charging System Power Bus Bar Alt Fld Alt Out Main Switch Alt Out Breaker Alt Fld Breaker Amp Meter Red OverVoltageSensor Black Main Solenoid Shunt Resister Orange LO/OV Light ALT + - Battery Alt Switch B I Voltage Regulator/ ACU S F A F

  7. Electrical Components • Voltage Testing Setup (Voltage On) • Master switch (Bat & Alt) - On • Alternator field switch – On • Alternator field and Main alternator breaker – On • To generate a load, turn landing lights on • Check Amp Meter with load on • If needle deflects, it is OK • If no deflection plus voltage on connections and shunt resistor, replace meter

  8. Voltage Regulator • With Voltage On, check voltage regulator pins • All pins should be close to Power Bus Bar voltage • If Pin S is low, check Over Voltage Sensor (OVS) connections • If OVS connections are good, OVS is bad • If Pin F is low • Disconnect Pin F to alternator lead • If Pin F is still low, replace Voltage Regulator • Regulator is shorted, also check if alternator field shorted • If Pin F is high, check alternator

  9. Voltage Regulator • If Pin A is low • Usually a connection problem • If Pin I is high and LV/OV light is out • Check bulb and wiring

  10. Alternator • Disconnect alternator leads and check alternator – voltage off • Check resistance between F (field lead) and ground connection • Range – 3 to 6 ohms • If low, field coil is shorted - replace alternator • If high • Service brushes and clean commutator • Resistance still high, field coil is broken - replace alternator

  11. Alternator • Check for open Stator by measuring resistance between B (battery lead) and ground • If high, stator is open and alternator needs to be replaced • Check for shorted diode bridge • Place a multi-meter in series with alternator B lead to measure leakage current • If leakage current is over 0.5 ma, bridge is bad – replace alternator

  12. Alternator • Check for open diode bridge • Power on, engine at 1500 RPM and lights on • Check AC voltage on B lead • If over 0.5 V, bridge is bad – replace alternator

  13. Alternator • Check alternator output • Install multi-meter to measure current in to F lead • If current is 3.5 A or higher and alternator output is still low, replace alternator • If still unable to determine problem, run external regulator test outlined in Alternator Test Regulator handout

  14. Finish Up • Do a final complete system test with engine running and lights on • Charge/test battery • Remember Diamond DA42 crash • Reinstall and tighten all components • Clean aircraft • Return aircraft in as-good or better shape than you received it • Complete logbook entry and work order

  15. Troubleshooting Steps • Setup • Connections • Electrical Components • Finish Up

  16. Topic • Solid State Voltage Regulators and Alternators • Most common solution • Piston engine • Not covered (because of time limitations) • Battery problems • Generators • Mechanical regulators • Turbine charging systems • Rebuild alternator

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