No-Load Test Hookup - Piper APACHE PA-23-235 Service Manual

PIPER AZTEC SERVICE MANUAL
11-106. TEST AND MAINTENANCE OF
STARTING MOTORS.
drag and it will not turn freely.
If the
armature does not turn freely, the mo-
tor should be disassembled immedi-
Figure 11-57. No-load Test Hookup
ately. However, if the armature does
operate freely, the motor should be given electrical tests before disassembly.
11-108. NO LOAD TEST. (Refer to Figure 11-57.) Connect the starting motor
in series with a fully charged battery of the specified voltage, an ammeter ca-
pable of reading several hundred amperes, and a variable resistance.
Also con-
nect a voltmeter as illustrated, from the motor terminal to the motor frame. An
RPM indicator is necessary to measure armature speed.
Obtain the specified
voltage by varying the resistance unit. Then read the current draw and the ar-
mature speed and compare these readings with the values listed in paragraph
11-114. Interpret the test results as follows:
a. Rated current draw and no load speed indicate normal conditionof the start-
ing motor.
b. Low free speed and high current draw indicate:
1. Too much friction - tight, dirty, or worn bearings, bent armature shaft
or loose pole shoes allowing armature to drag.
2. Shorted armature. This can be further checked on a growler after dis -
assembly.
c. Failure to operate with high current draw indicates:
1. A direct ground in the terminal or fields.
2. "Frozen" bearings (this should have been determined by turning the ar-
mature by hand).
d. Failure to operate with no current draw indicates:
1. Open field circuit. This can be checked after disassembly by inspec-
ting internal connections and tracing circuit with a test lamp.
ELECTRICAL SYSTEM