Piper Arrow IV, Maintenance Manual

Page: 201 / 752

ALTERNATOR SYSTEM (CHRYSLER).
BENCH TESTING ALTERNATOR.
ROTOR FIELD COIL CURRENT DRAW. (Refer to Figure 24-3.)
1. Connect a jumper wire between one field terminal of the alternator and the positive terminal of a fully
charged battery.
2. Connect the test ammeter positive lead to the other field terminal of the alternator and the test ammeter
negative lead to the battery negative terminal.
3. While watching the test ammeter, slowly rotate the alternator rotor by hand.
A. Field coil draw should be 4.5 to 6.5 amperes at 12-volts.
—NOTE—
A low rotor coil draw is an indication of high resistance in the
field coil circuit (brushes, slip rings or rotor coils). A higher rotor
coil draw indicates possible shorted rotor coil or grounded rotor.
B. No reading indicates an open rotor or defective brushes.
TESTING ALTERNATOR INTERNAL FIELD CIRCUIT.
To test the alternator internal field circuit for a short circuit to ground, proceed as follows:
1. Remove the ground brush and place one test probe of a 110-volt test lamp to the field terminal. Attach
the remaining test probe to a machined surface at one of the alternator end shields. The test lamp should not
light. (Refer to Figure 24-4.)
2. Should the test lamp light, proceed as follows:
A. Remove the insulated brush assembly.
B. Remove the three through bolts and separate the two end shield assemblies.
C. Touch one of the test lamp probes to one of the slip rings and the remaining test probe to the rotor
shaft. The lamp should not light. A lighted test lamp indicates a grounded rotor assembly and will
require replacement of the rotor. If the test lamp does not light, a ground condition exists in the
insulated brush assembly. The brush assembly has either been improperly assembled or was
damaged and has short circuited through to ground. Inspect brush holder and insulated washer and
replace if damaged.
—NOTE—
The stack of parts attaching the insulated brush holder assembly
to the end shield must always be installed in the following
sequence: Insulated brush holder, “FLD” terminal, insulating
washer, lock washer and attaching screw.
24-32-03
EFFECTIVITY: Page 24-14
CHRYSLER ALTERNATOR Revised: July 13, 1983
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PIPER AIRCRAFT
PA-28RT-201 / 201T
MAINTENANCE MANUAL