Piper Comanche PA-24 Service Manual page 701

PIPER COMANCHE SERVICE MANUAL
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FIGURE 9-27,. TESTING ROTOR
FOR GROUNDS
r'<'l
!----_
11---.,
RHEOSTAT'
PIGURE
9·2711.
TESTING ROTOR
FOR SHORTS
I
leld from one of the rectifiers in that heat siAl<. Then reverae tbe position of the leads. The
test bulb should lilht ill one direction and ""t Uabt in tlle otller direction.
If the
test bulb lieht.
in botb directions. one or
IDOte
at tlle teetifiers
in tbel heat .ink is shorted. To pinpoint tbe d ..
fective rectifier, the stator leads
IINSt
be
diSCDDllltcted
aDd the above test repeated
aD
each
teetifier. Open rectifiers can only be delecled. wllen IISinl the test bulb. by disconnecting tbe
stator leads. The tesl bulb will fail to light in eilber direction if the teCtilier is open.
c. Stalor: The stator can be tesled for open or graUllded winclines .,ilh a l2.volt test bulb.
described in the rectifier section. or an ohmmeter, in tbe foUowina manner. Separate the stator
&0"'
the slip nnl .nd head jllSt far enolllh to
insert
a fold
of
rap or blocks of wood. In otber
words. insulate the stator from the end heac!. To test for pounded windinls, touch one test bulb
or oh.,.,eter prabe to the .talor
&0.,.. If
tbe test bulb lights. or the ohmmeter indicales can·
tinu.ity. the stator is grounded.. To test for open wiadinp. coa_ct one test probe to the auxiliary
termuml or
the
stator wiodine center connectioD .ad touch each. of the three stator leads. The
test bulb must litht, or the ohmmeter m.ust show continuity. Due to the low resistance in the
stator windings, sharted windings are almost impcesible to locate. However, sborted stator
Windings will usually cause the alternator to up""l" or
be
DenBY during operatlon and will
usually show some lips of overheatina. U all otber electrical checks are normal and the al ...
ternator falls to supply lts rated output, the stator should be replaced. to deterlll1ne whether or
not it is the faulty component.
d. Bearinp and Seais: Whenever the allemalor ;. overheuled. new be.rines ancl oilor grease
seals are recommendecl. evea though the
be.rinas and seals appear to be in good. corMiition. A
faulty seal can cause Ie alternator to fail within a very shan period. of time.
3 Cl
EleCTRICAL SYSTEM
ISSUED: 8I1Sn2