Piper Cherokee Six - Page 573

365
365
RHEOSTAT
AMMETER
ROTOR
BATTERY
VOLTMETER
Figure
1 0-24f. Testing Rotor
for Ground
Figure 10-24g.
Testing Rotor for
Shorts
other
direction.
If the
test bulb
lights
in both
directions,
one
or more
of the
rectifiers
in
that
heat
sink is
shorted.
To
pinpoint
the
defective
rectifier,
the
stator
leads
must
be
disconnected
and
the above
test
repeated
on each
rectifier.
Open
rectifiers
can
only
be
detected,
when
using
the test
bulb,
by disconnecting
the
stator leads.
The
test bulb
will
fail
to light
in either
direction
if the rectifier
is open.
c. Stator:
The
stator
can be
tested
for open
or grounded
windings
with
a 12
volt test
bulb,
described
in
the rectifier
section,
or
an ohmmeter,
in the
following
manner.
Separate
the stator
from the
slip
ring end
head
just
far enough
to insert
a fold
of
rags or
blocks
of
wood.
In other
words,
insulate
the
stator
from
the end
head.
To
test for
grounded
windings.
touch
one
test bulb
or ohmmeter
probe
to the
auxiliary
terminal
or any
stator
lead, and
the
other
test
bulb
or ohmmeter
probe
to
the stator
frame.
If the
test bulb
lights,
or
the
ohmmeter
indicates
continuity,
the
stator
is grounded.
To
test for
open
windings,
connect
one
test
probe
to the
auxiliary
terminal
or the
stator
winding
center
connection
and
touch
each
of the
three
stator
leads.
The
test bulb
must
light,
or
the
ohmmeter
must
show
continuity.
Due to
the low
resistance
in the
stator
windings,
shorted
windings
are
almost
impossible
to locate.
However,
shorted
stator
windings
will
usually
cause
the
alternator
to
"growl"
or be
noisy
during
operation
and
will
usually
show
some
signs of
overheating.
If all
other
electrical
checks
are normal
and alternator
fails
to supply
its
rated
output,
the
stator
should
be replaced
to determine
whether
or
not it
is the
faulty
component.
d. Bearings
and Seals:
Whenever
the
alternator
is overhauled,
new
bearings
and
oil
or
grease
seals
are recommended,
even
though
the bearings
and
seals
appear
to be
in good
condition.
A faulty
seal
can cause
an
alternator
to fail
within
a very
short
period
of time.
ELECTRICAL
SYSTEM
Issued: 8/17/72
PIPER
CHEROKEE
SIX
SERVICE
MANUAL
3B21