Testing Stator Coils For Ground; Testing Alternator Capacitors - Piper Cherokee Six Service Manual

PIPER CHEROKEE SIX SERVICE MANUAL
10-14. TESTING STATOR COILS FOR GROUND. The stator coils are insulated
from the core. A break in the insulation allowing the bare wire to touch the core
will ground the coil and result in no output.
To test the stator for a ground (end shields separated), lift the stator away
from the end shield and place wooden blocks approximately .50 inch thick between
the stator and the shield to keep them separated.
Using a 110volt test lamp, place one test probe on the core and the other
test probe to one of the rectifier leads, making certain to have good electrical
connections at both test probes. The lamp should not light. If the lamp lights,
it is an indication that the coil windings are grounded to the core and a replace-
ment of the stator is required.
10-15. TESTING ALTERNATOR
CAPACITORS. Capacitors are used in connec-
tion with alternators to suppress any transient peak voltage that may occur. It
is essential therefore, to test the capacitor
when servicing the alternator.
This is especially true where diode rectifiers test open or short circuited.
The capacitor is connected to the inner end of the alternator "BAT" term-
inal screw and to the inner surface of the rectifier end shield (ground).
NOTE
On some early models, the capacitorwas installed on
the outside.
Connect the capacitor tester to the alternator
"BAT" terminal screw and
the disconnected
ground lead.
CAUTION
Do not allow thetesterprobes or clips to touch the end
shield or the rectifier leads while the test is in pro-
gress or damage to the rectifiers may occur.
Specified capacity for alternator capacitors of the early models is as follows:
Internally mounted .158 MFD (min.)
Very early external mount .5 MFD (min.)
The specified capacity for later built alternators (capacitor part of ter-
minal screw) is .5 + .1 MFD (min.).
Replace capacitors with low capacity, shorted or with high series resist-
ance.
ELECTRICAL
SYSTEM
Issued: 8/17/72
3B6