Piper Comanche PA-24 Service Manual page 667

PIPER
COMANCHE SERVICE MANUAL
f. Burned Relay Contact Points - This is due to rever.ed generator polarity Generator polarity must
be corrected as explained in (Paragraph 9-29.e) after any checks of the regulator or generator. or after dis-
connecting and reconnecting lead,.
9-6. Adjustments. Tests And Maintenance
or
Generator. IDelco-Remy)
a. The best assurance of obtaining maximum service from generators with minimum trouble. is to
follow a regular inspection and maintenance procedure Periodic lubrication where req uired. in-spection of the
brushes and commutator. and checking of the brush spring tension are essentials in the inspection procedure
In addition. disassembly and thorough overhauling of the generator at periodic intervals are desirable as a
safeguard against failures from accumulations of dust and grease and normal wear of pans. This is particularly
desirable on installations where maintenance of operating schedules is of special importance. In addition to
the generator itself. the external cirCUits between the generator. regulator and battery must be kept in good
condition since defective "iring or loose or corroded connections will prevent normal genera tor and regulator
action
9-7. Inspection.
a. At periodic intervals. the generator should be inspected to determine its condition The frequenc\
with which this should be done will be determined by the type of service in which it is used High speed
operation. excessive dust or dirt. high temperatures and operating the generator at or near full output most
of the time are all factor. which increase bearing. commutator. and brush wear. Generally speaking. the units
should be impected at approximately 100 hour intervals The inspection procedure follows
b First. inspect the terminals. external connections and wiring. mounting. pulley and belt Then
remme the cover band so that the commutator. brushes and internal connections can be inspected If the
commutator is dirty. it may be cleaned with a strip of
~o.
00 sandpaper. I"ever use emery cloth to clean the
commutator
c. The sandpaper may be used by holding it against the commutator with a wood stick ... hile the
generator is rotated. moving it back and forth across thecommutator. Gum and dirt will be sanded offin a few
seconds. All dust should be blown from the generator after the commutator has been cleaned A brush seating
stone can al;o be used to clean the commutator
d If the commutator is rough. out of round. or has high mica. the generator must be remm'ed and
disassembled so that the armature can be turned down in a lathe a-nd the mica undercut
e. If the brushes are worn down to less than half their original length. they should be replaced.
Compare the old brush with a new one to determine how much it is worn "ew brushes should be seated to
make sure that they are in good contact With the commutator A convenient tool for seating brushes isa brush
seating or bedding stone This is a soft abrasive material which: when held against a revolving commutator.
disintegrates so that particles are carried under the brushes and wear their contacting faces to the contour of
the commutator in a few seconds. All dust should be blown from the generator after the brushes are seated.
f.
The brush spring tension (24 oz ) must be correct since excessive tension will cause rapid brush and
commutator wear. while low tension causes arcing and burning of the brushes and commutator. Brush spring
tension can be checked with a spring gauge hooked on the brush arm or brush attaching screw. Correction
can be made by bend ing the brush spring as required. If the brush spring shows evidence of overheating (blued
or burned). do not attempt to readjust it. but install a new spring. Overheating will cause a spring to lose its
temper
g The belt should be checked to make sure that it is in good condition and has correct tension. Low
belt tension will permit belt slippage with a resulting rapid belt wear and low or erratic
ISSUED: 8/18/82
3A15
ELECTRICAL SYSTEM