Piper Cherokee Six - 10-27 A. Alternator System (Prestolite)

PIPER
CHEROKEE
SIX
SERVICE
MANUAL
10-27a.
ALTERNATOR
SYSTEM
(PRESTOLITE).
10-27b.
CHECKING
ALTERNATOR
SYSTEM.
With
all
electrical
equipment
off
(except
master
switch)
the
ammeter
will indicate
the amount
of charging
current
demanded
by
the
battery.
This
amount
will
vary,
depending
on
the percentage
of
charge
in
the battery
at the
time.
As
the battery
becomes
charged,
the
amount
of
current
displayed
on
the ammeter
will
reduce
to
approximately
two
amperes.
The
amount
of current
shown
on
the ammeter
will
tell
immediately
whether
or not
the
alternator
system
is operating
normally,
if the
following
principles
are kept
in
mind.
NOTE
The amount
of
current
shown
on the ammeter
is the load
in
amperes
that is
demanded
by
the
electrical
system
from
the
alternator.
As
a check,
take
for
example
a condition
where
the battery
is demanding
10 amperes
charging
current,
then
switch
on
the landing
light.
Note
the value
in amperes
placarded
on
the
circuit
breaker
panel
for
the
landing
light
circuit
breaker
(10
amps)
and
multiply
this
by 80
percent,
you will
arrive
at
a current
of 8
amperes.
This
is
the
approximate
current
drawn
by the
light.
Therefore,
when
the
light
is switched
on,
there will
be
an increase
of
current
from
10 to
18 amperes
displayed
on
the ammeter.
As each
unit of
electrical
equipment
is switched
on,
the current
will
add up
and
the
total, including
the battery,
will
appear
on the
ammeter.
Using
the example
that
the airplane's
maximum
continuous
load with
all equipment
on
is
approximately
48
amperes for
the 60 ampere
alternator.
This approximate
48 ampere
value.
plus approximately
two amperes
for
a fully charged
battery,
will
appear continuously
under
these flight
conditions.
If
the ammeter
reading
were to
go much
below this
value, under
the
aforementioned
conditions.
trouble
with the
alternator
system
would
be indicated
and
corrective
action should
be taken by switching
off the least
essential equipment.
The following
test
procedure
could be helpful
in locating
faulty
components:
a. Ascertain
that the
airplane is
positioned so
that the prop
blast will
not interfere
with
other operations
going
on near by.
Start engine
and set throttle
for 1000
to 1200
RPM.
b.
Switch on the
following
loads and observe
the ammeter
output
increase as
indicated.
1. Rotating beacon - 3 to 6 amps.
2.
Navigation and
instrument
lights (bright
position) - 4 to
6 amps.
3.
Landing light
- 7 to 9 amps.
If
alternator
does not meet
above indications,
refer
to troubleshooting
chart. Follow
troubleshooting
procedure
outlined on
the chart in
a step by
step fashion
checking each
cause
and isolation
procedure under
a given trouble before
proceeding
to the next.
On airplanes
without
night-flying
equipment,
load required
by test
can be simulated
by
connecting
a lamp-bank
load consisting
of
8 landing
lights wired
in parallel
from
main bus
(+) to
airframe ground
(-) (Refer
to Figure
10-3)
or 3 ohm,
100 watt resistors.
ELECTRICAL
SYSTEM
Revised:
8/14/73
3B16