Mooney M20TN, Руководство по обслуживанию и ремонту

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MOONEY AVIATION COMPANY, INC.
M20TN SERVICE & MAINTENANCE MANUAL
Page
Date
11
2006
Rev Date
tween Terminal 5 of the regulator and the field terminal.
If an open field circuit is suspected, the switches may
be turned off, the alternator field connector removed,
and a resistance measurement made between the con-
nector and Terminal 5 of the regulator. Look for near 0
Ohms. Typically the field resistance of the alternator
will be between 3 and 10 Ohms from the male field ter-
minal blade to alternator case.
Field Terminal Voltage ______v
Alternator field resistance ______
Ω
6. With the switches on, check the voltage between
the alternator output post (or
S
B
S
lead) and ground. It
should be battery voltage. If not, check the wiring be-
tween the alternator
S
B
S
lead and the battery positive
(+) terminal. Look for loose or contaminated connec-
tions, broken wires, or an open breaker or fuse.
Alternator
S
B
S
Voltage ______v
7. If all of the voltages in the first 6 steps are close to
the value specified, the charging system should be op-
erative. If not, check for a broken or loose alternator belt
or, if the alternator is spline driven, check that the spline
drive shear coupling is not sheared. Note that on spline
drive alternators the engine speed must be at or above
run--up RPM before checking for useable output.
NOTE:
During the following tests, if the annunciator is
always ON or always OFF, check the annunciator
circuit by removing the wire from terminal 2 of
the regulator. The lamp should be OFF with the
wire disconnected and should illuminate if the
wire is connected to ground.
If the lamp circuit works properly but the lamp still re-
mains fixed either ON or OFF all the time with the lamp
wire connected to Terminal 2, assume that the lamp
driver is bad in the regulator. Have the regulator re-
paired or replaced.
If the charging system seems to be generating power,
but the STBY ALT ON annunciator will not flash above
20 amps output, check the following:
8. With the Battery and Standby Alternator Master
switches ON but the engine not running, check the volt-
age between terminals 4 and 7 of the regulator. The
voltage should be 10.0,
±
0.1 volts. If it is not within tol-
erance, remove the wire from Terminal 4 and re--check
the voltage. If it is still not within tolerance the regulator
may be bad. If the voltage is now in tolerance, suspect a
bad current sensor or shorted sensor wire.
9. If the voltage originally measured in step 8 was in
tolerance, divide the measurement by 2. This value
should be the voltage measured between terminals 3
and 7 of the regulator. If the voltage measured is not
close to 5.0 Volts, suspect the current sensor in the
standby alternator output lead.
10. If the measurements in Steps 8 and 9 are satis-
factory, prepare to monitor the voltage between termi-
nals 3 and 7 of the regulator with the engine running.
Move the aircraft to a safe location for a 2000 RPM run-
up. Start the engine. Minimize the bus loads and bring
the engine RPM up to approximately 2000. Switch OFF
the primary alternator. Wait for the STBY ALT ON an-
nunciator to illuminate. At light bus loads this could take
a minute or two. Note the voltage between terminals 3
and 7 of the regulator and begin switching ON addition-
al bus load. The monitored voltage should increase at
the rate of 0.056 Volts for each Amp of standby alterna-
tor load.
a.) If the voltage does not change, verify standby
alternator output with the ship’s ammeter or a clamp--
on ammeter probe. If the standby output is verified and
there is still no change in the monitored voltage, sus-
pect a bad current sensor.
b.) If the voltage decreases instead of increasing,
the 10 Ga. current sensor wire is connected backward.
Reverse the connection and re--run the test.
c.) If the voltage increases at approximately the
correct rate, continue adding load until the voltage is
greater than 6.2 volts. At or above this voltage, the lamp
should be flashing. If not suspect a bad regulator.
TROUBLESHOOTING -- NOISE (STANDBY ALT.)
Noise problems are also difficult to find. A few tips to
help with curing noise problems follow:
1. A unitized grounding system helps prevent noise
problems by preventing voltage differences between
different ground points.
2. The battery acts as a noise filter in the system.
Poor connections to the battery or a battery that is going
bad can add to or even cause noise problems.
3. Shielding of low level audio leads (especially mi-
crophone leads or headset leads) is required. Some-
times the shields in the cables can separate from re-
peated flexing. Try checking shield continuity with an
ohmmeter or substituting another headset, micro-
phone, etc.
4. Wire routing may be important in some installa-
tions. Separation of noise carrying conductors such as
S
P
S
leads from other wiring may help. Running noisy
wiring parallel to other wiring in the same bundle is ask-
ing for trouble. Wires at 90 degrees to one another,
however, do not couple noise.
5. Running transmitter feed lines close to and in par-
allel with other wiring can cause a problem. Normally,
problems will only be encountered if there is a mis-
match and therefore a high SWR in the antenna sys-
tem. If noise or charging system breaker tripping oc-
curs during Comm transmit only or when the
transponder is on only, check the corresponding anten-
na system carefully or separate the transmission line
from other wiring.
24--31--03
AUGUST 2010