Piper Navajo PA-31 Service Manual page 718

stud and is insulated from ground.
The brush holder assembly can easily be
removed for inspection
or brush replacement purposes.
b. The slip ring end head provides the mounting
for the rectifiers
and recti-
fier mounting plate, output and auxiliaryterminal
studs, and thebrush
and holder
assembly.
The slip ring end head contains a roller bearing
and outer race as-
sembly and a grease seal.
c. The rectifiers
used in these units are rated at 150 peak inverse
voltage
(PIV) minimum for transient
voltage protection. Three positive rectifiers
are
mounted in the rectifier mounting plate while the three negative rectifiers
are
mounted in the slip ring end head. Each pair of rectifiers
is connected to a
stator lead with high temperature
solder. The stator leads are anchored to the
rectifier mounting plate with epoxy cement for vibration protection.
d. The stator contains
a special lead which is connected to the center of the
three phase windings and is used to activate
low voltage warning systems
or re-
lays. The stator has been treated
with a special epoxy varnish for high temper-
ature resistance.
e. The rotor contains the slip ring end bearing
inner race and spacer on the
slip ring end of the shaft. The rotor winding and winding leads have been specially
treated with a high temperature
epoxy cement to provide vibration
and temper-
ature resistance characteristics.
High temperature solder is used to secure the
winding leads to the slip rings.
f. The drive end head supports a sealed, prelubricated
ball bearing in which
the drive end of the rotor shaft rotates.
11-27. CHECKING ALTERNATOR SYSTEM. The ammeter
is equipped with two
selector switches whichenable an independent output check of each alternator,
as
well as the electrical output-input
of the battery. Should either alternator
show
no output on the ammeter,
check the appropriate circuit breakers. If a further
check of the ammeter shows no output from both alternators,
switch to the aux-
iliary voltage regulator and overvoltage
relay. If switching to the auxiliary sys-
tem indicates
no electrical output, further check the alternator
system. (Refer
to Figure 11-17.)
a. Ascertain that the ammeter is operating properly.
b. Disconnect the battery lead (+) at the alternator.
c. Disconnect fields (F1 and F2) leads at the alternator.
d. Ascertain
that all electrical units are off and battery is fully charged.
e. Turn on the master switch.
f.
To check the alternator output circuit,
connect a voltmeter or 24-volt test
light to the battery lead and to ground.
If a reading of approximately 24-volts
registers
on the voltmeter or the test light lights, the battery circuit
is oper-
ational.
Reissued: 10/12/79
ELECTRICAL SYSTEM
Effectivity
PRESTOLITE
4B16
4B16
PIPER NAVAJO SERVICE MANUAL