Troubleshoo*ng Aircra2 Charging Systems

by Herb Spenner

Teaching Environment Documents on line

Lecture, handouts, worksheets and manuals General loca*on - hhh.gavilan.edu/hspenner This lecture hhh.gavilan.edu/hspenner/05-16-11

Expect students to take notes - slower pace References to class text books

Reword for beNer understanding

Topic Solid State Voltage Regulators and Alternators

Most common solu*on Piston engine

Not covered (because of *me limita*ons) BaNery problems Generators Mechanical regulators Turbine charging systems Rebuild alternator

Cheaper to buy a new or rebuilt unit

Troubleshoo*ng Steps 1. Setup 2. Connec*ons 3. Electrical Components 4. Finish Up

Setup Avionic must be turned o

Protects them from damage Master switch On when checking voltage Master switch O when checking resistance

Select mul*-meter range before measuring Secure item before running engine

Connec*ons Check circuit breakers

If tripped, nd out why Remind customer of Special Airworthiness Informa*on Bulle*n (SIAB) CE 11-10 Electrical: Fire Hazard in Reseang Circuit Breakers

Check grounding straps Refer to AC 43.13-1B 11-188 Use Low Ohm Meter (LMO) to check connec*ons

Standard mul*-meter not sensi*ve enough See Prac*cal Low Resistance Measurement Bob Neckolls

Connec*ons Check all mechanical connec*ons are *ght Cleanup all corrosion Check for damaged insula*on Recommend customer replace old aluminum baNery cable BeNer cold starts Save money through longer component life

Check alternator belt Insure alternator bearings work smoothly

Typical Charging System

ALT

Power Bus Bar Alt Out Alt Out Breaker

B

Main Solenoid

Shunt Resister

Amp Meter

BaNery

+

-

Over Voltage Sensor

Red

Orange B

lack

Alt Fld

Alt Fld Breaker

Voltage Regulator/

ACU

S

Alt Switch

A

F

F

LO/OV Light

I

Main Switch

Electrical Components Voltage Tes*ng Setup (Voltage On)

Master switch (Bat & Alt) - On Alternator eld switch On Alternator eld and Main alternator breaker On To generate a load, turn landing lights on

Check Amp Meter with load on If needle deects, it is OK If no deec*on plus voltage on connec*ons and shunt resistor, replace meter

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) connec*ons If OVS connec*ons are good, OVS is bad

If Pin F is low Disconnect Pin F to alternator lead If Pin F is s*ll low, replace Voltage Regulator

Regulator is shorted, also check if alternator eld shorted

If Pin F is high, check alternator

Voltage Regulator If Pin A is low

Usually a connec*on problem If Pin I is high and LV/OV light is out

Check bulb and wiring

Alternator Disconnect alternator leads and check alternator voltage o

Check resistance between F (eld lead) and ground connec*on Range 3 to 6 ohms If low, eld coil is shorted - replace alternator If high

Service brushes and clean commutator Resistance s*ll high, eld coil is broken - replace alternator

Alternator Check for open Stator by measuring resistance between B (baNery lead) and ground If high, stator is open and alternator needs to be replaced

Check for shorted diode bridge Place a mul*-meter in series with alternator B lead to measure leakage current

If leakage current is over 0.5 ma, bridge is bad replace alternator

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

Alternator Check alternator output

Install mul*-meter to measure current in to F lead If current is 3.5 A or higher and alternator output is s*ll low, replace alternator

If s*ll unable to determine problem, run external regulator test outlined in Alternator Test Regulator handout

Finish Up Do a nal complete system test with engine running and lights on

Charge/test baNery Remember Diamond DA42 crash

Reinstall and *ghten all components Clean aircra2

Return aircra2 in as-good or beNer shape than you received it

Complete logbook entry and work order

Troubleshoo*ng Steps 1. Setup 2. Connec*ons 3. Electrical Components 4. Finish Up