Unsteady Or Low Output Of The Generator; Excessive Output Of The Generator; Noisy Generator - Piper PA-24 Comanche Service Manual

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PIPER COMANCHE SERVICE MANt;AL
the armature core). The steel st rip will vibrate above the area of the armature core in which short circuited
armature coils are located. If the short circuit is obvious. it can often be repaired so that the armature can be
saved.
9-11.
rnstead~'
Or Low Output. If the generator produces a low or unsteady output. the following
factors
should be considered:
a. A loose drive belt will ..lip and cause a low or unsteady output.
b. Brushes which stick in their holders. or low brush spring tension will prevent good contact between
the brushes and commutator so that output will be low and unsteady. This will also cause arcing and burning
- of the brushes and commutator.
c. If the commutator is dirty. out of round. or has high mica. generator output is apt to be low and
unsteady. The remedy here is to turn the commutator down in a lathe and undercut the mica. Burned
commutator bars may indicate an open circuit condition in the armature as already stated above. (Refer to
Paragraph 9-10.)
9-12. E
xcessive Output.
a. When a generator produces excessive output on an application. the procedure for determining
whether the trouble is in the generator. regulator. or elsewhere is outlined in Paragraph
9-5.
If the generator
output remains high. even with the
"F"
terminal lead disconnected. then the trouble is in the generator itself.
and it must be further analvzed to locate the source of trouble.
b.
In the system which has the generator field circuit grounded externally. accidental internal
grounding of the field circuit would prevent normal regulation so that excessive output might be produced
by the generator. On this type of unit. an internally grounded field which would cause excessive output
may
be located by use of test points connected between the
"F"
terminal and the generator frame. Leads should be
disconnected from the "F' terminal and the brush to which the field lead is connected inside the generator
should
be
raised from the commutator before this test is made.
If
the lamp lights. the field is internally
grounded. If the field has become grounded because the insulation on a field iead has worn away. repair can be
made by
reinsulating the lead. It is
also possible to make repair where the ground has occurred atthe pole shoes
by removing the field coils and reinsulating and reinstalling them. A ground at the "F" terminal stud can be
repaired by installing new insulating washers or bushings.
~OTE
If
battery temperature is excessive. battery overcharge is apt to
occur. even though regulator settings are normal. Under this condi-
tion. it is permissible to reduce the voltage regulator setting as
explained in the applicable bulletin pertaining to the regulator used
on the application .
. 9-
1.:\.
l'ioisy Generator. Noise emanating from a generator may be caused by a loose mounting. drive pulley.
or gear: worn or
dirty
bearings: or improperly seated brushes.
Dirty
bearings may sometimes be saved
b~
cleaning and relubrication, but worn bearings should be re-laced. Brushes can be seated as explained in
Paragraph 9-7.
If
the' brush holder is bent. it may be difficult to reseat the brush so that it will function
properly without excessive noise. Such a brush holder will require replacement.
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ISSl"ED: 8/18/72
3A18
ELECTRICAL SYSTE1\t