Mooney M20TN, Service And Maintenance Manual

Page: 197 / 1169

MOONEY AVIATION COMPANY, INC.
M20TN SERVICE & MAINTENANCE MANUAL
Page
Date
5
2006
Rev Date
24--00--00 -- GENERAL
Main Alternator System
A 28 volt, 100 AMP alternator (90 amps max. output)
utilizing a transistorized voltage regulator/over voltage
control supplies electrical power for the main alternator
source. Two 24 volt, 10 AMP HR storage batteries are
installed in the tailcone. The alternator, during normal
operation, supplies power in conjunction with the se-
lected battery when the Master Switch and Alternator
Field Switch is -- ON. The circuit breaker panel is on the
right subpanel. The electrical system is capable of sup-
plying current for simultaneous operation of multiple ra-
dios, anti--collision lights and navigation lights.
Standby Alternator System
An optional standby system provides 30 volts, with 20
amps of power to support continued flight in the event of
primary alternator failure. The Standby alternator is
installed on the accessory pad location. Panel mounted
equipment includes a STBY ALT ON annunciator and
two standard pull type circuit breakers (1 amp and 5
amp) and a STBY ALT master switch. Appropriate plac-
ards are provided for each panel mounted device. The
regulator is mounted in the RH nosegear wheelhouse
area on the M20TN Aircraft. If the primary alternator
fails in flight, the pilot activates the standby alternator. If
the current requirement is over 26.5 volts when the
standby alternator is activated, the annunciator will
flash. The pilot is advised to choose which equipment
he needs for the given flight conditions by simply keep-
ing the total load below the flashing point of the annun-
ciator. This will reserve battery energy for transient
loads during approach (refer to the M20TN POH/AFM
for specific equipment limitations) . Loads may be
beyond the flashing point of the annunciator for up to 5
minutes without damaging the standby alternator.
NOTE:
The standby alternator system is required equip-
ment for the installation of the certified flight into
known icing TKS STC kit on the M20TN aircraft.
GARMIN G1000 (S/N 31--0001 THRU 31--TBA)
Refer to Garmin G1000 Maintenance Manual for elec-
trical system status and displays.
24--30--00 -- D.C. GENERATION
24--31--01 -- CHARGING SYSTEM MAINTENANCE
MAIN ALTERNATOR
1. Alternator Systems Servicing
When the ammeter (Garmin G1000 MFD display)
shows a discharge at higher RPM, a charging system
component (alternator, voltage regulator, circuit break-
er or wiring) is malfunctioning. On--the--plane testing
should identify which component(s) may be faulty and
needs to be removed from the aircraft for bench test
and subsequent repair or replacement.
The alternator charging system requires no special
attention; however, improper maintenance procedures
can damage the alternator and wiring. There are sever-
al precautions that must be observed when servicing
the alternator system:
A. Be sure the Master Switch is OFF when repair-
ing the alternator or voltage regulator.
-- CAUTION --
Only when performing functional checks on
ground, First connect the approved Auxiliary
Power Cable to the booster battery and then in-
sert the plug into the auxiliary power receptacle.
B. Refer to 24--31--04 for Auxiliary Power System
instructions.
-- CAUTION --
Both batteries MUST BE in aircraft for flight.
C. When either battery is removed from the aircraft
for charging, be sure that the charger is correctly con-
nected. Use the correct charging rate when charging
battery, refer to manufacturer’s procedures.
D. Be sure to check battery polarity by using a volt-
meter prior to reinstallation into the aircraft.
E. Do not leave Master Switch ”ON” when aircraft
is parked.
F. Use an auxiliary ground power unit when trou-
bleshooting electrical accessory equipment or when
performing electrical landing gear maintenance and re-
traction system testing.
-- CAUTION --
DO NOT ATTEMPT TO POLARIZE ALTERNATOR.
Alternator is polarized every time Master Switch
is turned ON causing wire lead to Alternator to
become energized “Live Wire”.
2. Alternator System Inspection
A. Check alternator circuit breaker on the main cir-
cuit breaker panel. Reset breaker, if open.
B. Check alternator field circuit breaker on main
circuit breaker panel. Reset, if open.
C. Inspect batteries for corroded cable connec-
tions; remove and clean cable(s) if corrosion is found.
D. Check charging system wiring and connectors
to be sure they are clean and tight.
E. Inspect alternator, voltage regulator, and wiring
for damage.
3. Alternator Removal and Installation
A. Alternator Removal
(1) Turn Master Switch OFF. Disconnect alterna-
tor wiring.
(2) Remove attaching hardware and pull alterna-
tor drive gear from engine pad.
B. Alternator Installation
(1) Be sure Master Switch is turned -- OFF. Do
not turn Master Switch ON until all wiring connections
have been secured.
24--00--00
AUGUST 2010