Piper Navajo PA-31 Service Manual page 726

NOTE
Always refer to the wiring diagram (Refer to Figure
11-17.) when installing the alternator or testing the
alternator.
11-34. PRECAUTIONS. The following precautions are to be observed when test-
ing or servicing the electrical system.
a. Disconnect
the battery before connecting or disconnecting test instruments
(except voltmeter) or before removing or replacing any unit or wiring.
Acciden-
tal grounding or shorting at the regulator, alternator, ammeter or accessories,
will cause severe damage to the units and/or wiring.
b. The alternator
must not be operated on open circuit with the rotor winding
energized.
c. Do not attempt to polarize the alternator. No polarization is required.
Anyattempt todo so mayresult in damage tothe alternator, regulatoror circuits.
d. Grounding of the alternator output terminal may damage the alternator and/
or circuit and components.
e. Reversed battery connections may damage the rectifiers, wiring or other
components of the charging system. Battery polarity should be checked with a
voltmeter before connecting the battery. Most aircraft
are negative ground.
f. If a booster battery or fast charger
is used, its polarity must be connected
correctly to prevent damage to the electrical system components.
11-35. ALTERNATOR NOMENCLATURE.
a.
Bearings: These units have a sealed ball bearing at the drive end and a
two-piece roller bearing at the slip ring end. The inner race is pressed onto the
rotor shaft and the rest of the bearing is in the slip ring end head. When the unit
is assembled, the inner race aligns with the bearing. When the bearing is re-
placed, the new inner race must be installed on the rotor shaft.
b.
Lubrication: The slip ring end bearing should be lubricated whenever the
alternator is disassembled.
The bearing should be thoroughly cleaned and re-
packed with Shell Alvania No. 2 or an equivalent bearing lubricant. The cavity
behind the bearing should be packed one-third to one-half full with the same
lubricant.
c. Brushes:
These units have a separate brush holder assembly that is in-
stalled after the alternator has been assembled. The brush holder has a small
hole that intersects the brush cavities. Use a pin or a piece of wire, as shown
in Figure 11-29, to hold the brushes
in the holder during assembly. Remove the
pin after the brush holder retaining screws have been tightened.
Make a contin-
Reissued: 10/12/79
ELECTRICAL SYSTEM
Effectivity
PRESTOLITE
4B24
PIPER NAVAJO SERVICE MANUAL