Piper Cherokee Six - Page 583

PIPER
CHEROKEE
SIX SERVICE
MANUAL
AMMETER
fied voltage
by
varying
the resistance
unit.
Then read the
current draw and
armature
speed
and compare these
readings
with the
values
listed
in the
published
specifications.
Interpret
the
test
results
as follows:
a. Rated current
draw and
no-load
speed
indicate normal
condition of
the
cranking motor.
b. Low free speed
and high
current
draw indicate:
1. Too much
friction-tight,
dirty,
or loose
pole shoes
allowing
armature
to drag.
2. Shorted
armature.
This can
-be further checked
on a growler
after
disassembly.
3. Groundedarmature
or fields.
CRANKING MOTOR
Figure
10-26. Resistance
Test
Check further
after disassembly.
c.
Failure
to operate
with
high current
draw
indicates:
1. A
direct
ground
in the
terminal
or fields.
2. "Frozen"
bearings
(this
should have
been determined
by turning
the ar-
mature
by hand).
d. Failure
to
operate
with no
current
draw
indicates:
1. Open field
circuit.
This can
be checked
after disassembly
byinspecting
internal
connections
and tracing
circuit
with
a test
lamp.
2. Open
armature
coils.
Inspect
the
commutator
for
badly
burned
bars
after disassembly.
3. Broken
brush
springs,
worn
brushes,
high
insulation
between
the
com-
mutator
bars or
other causes
whichwould
prevent
good contact
between
the brushes
and commutator.
e.
Low no-load
speed
and
low current
draw
indicate:
1. High internal
resistance
due
to poor connections,
defective
leads, dirty
commutator
and causes listed
under (d).
f. High
free speed
and high
current draw
indicate
shorted
fields. If
shorted
fields are
suspected,
replace the
field coil
assembly and
check for
improved
per-
formance.
10-40. RESISTANCE
TEST.
(Refer to Figure
10-26.) This
test requires that
the pinion be locked
securely so
it cannot rotate.
When the specified
voltage is
applied,
the current
should
fall ina
range as indicated
inpublished
specifications.
ELECTRICAL
SYSTEM
Issued: 8/17/72
3C7