Piper Navajo PA-31 Service Manual page 704

PIPER NAVAJO SERVICE MANUAL
CAPACITOR
HEAT SINK
Figure 11-4. Cross-Sectional View Alternator (Delco)
The winding is checked for short circuits
by connecting a battery and am-
meter
in series with the two slip rings.
Note the ammeter reading and refer to
paragraph 11-19 for specifications.
An ammeter
reading above the specified
value indicates shorted windings.
An alternate method is to check the resistance
of the field by connecting
an ohmmeter to the two slip rings.
(Refer to Figure
11-5.) If the resistance
reading is below the specified
value, the winding is
shorted. The specified
resistance value can be determined
by dividing the volt-
age by the current
given in paragraph 11-19.
If the rotor is not defective,
and
the alternator
fails to supply rated output when checked as covered in the section
entitled Output Check,
the trouble is in the stator or rectifying
diodes.
STATOR CHECKS: To check the stator
windings,
remove all three stator lead
attaching nuts (Refer
to Figure 11-7) and then separate
the stator assembly
from the end frame.
The fit between stator
frame and end frame is not tight,
and the two can be separated
easily.
The stator windings may be checked with a 110-volt test lamp or an ohm-
meter. If the lamp lights, or if the meter
reading is low when connected from
any stator
lead to the frame, the windings are grounded.
If the lamp fails to
light, or if meter
reading is high when successively
connected between each pair
of stator leads, the windings are open.
(Refer to Figure 11-8.)
A short circuit
in the stator windings is difficult to locate without labora-
tory test equipment
because of the low resistance
of the windings. However, if
all other electrical
checks are normal and the alternator
fails to supply rated
output,
shorted stator windings
are indicated. Also, another possibility
is a
Reissued: 10/12/79
ELECTRICAL
SYSTEM
Effectivity
4B2
DELCO