Bench Tests; Starting Motor Control Circuit - Piper Navajo PA-31 Service Manual

PIPER NAVAJO SERVICE MANUAL
NOTE
The spring tension is 32 to 40 ounces with new brushes.
This tension is measured
with the scale hooked under
the brush spring near the brush andthe reading is taken
at right angles to the line of force exertedby the brush
spring.
c. Check the positionof the pinion to be sure the unit will mesh properly
with
the flywheel ring gear.
See specifications for unit for correct dimensions.
Refer to paragraph 11-74.
11-72. BENCH TESTS.
a. After the starting motor is reassembled, it should be tested to see that the
no-loadcurrent at acertainvoltage is within specifications asgiven in paragraph
11-74. To make this test, connect as shown in Figure 43. If current
is too high,
check the bearing alignment and end play to make sure there
is no binding or
interference. Two or three sharp raps on the frame with a rawhide hammer will
often help to align the bearings
and free the armature.
b. If no difficulty is indicated in the above test, a stall torque test may be
made to see if the starting
motor is producing its rated cranking power. Make
test connections as shown in Figure 11-44.
c. If torque and current are not within specifications,
check the seatingof the
brushes and internal connections
for high resistance. If these checks are made
and found to be in good order, replace frame and field assembly
and retest
starter.
11-73. STARTING MOTOR CONTROL CIRCUIT.
a. Inspect the control circuit
wiring between the battery, solenoid and manual
starting switches for breaks,
poor connections and faulty insulation. Tighten
all connections
and make sure solenoid is firmly mounted and makes a good
ground connections.
b. Check the voltage loss across
the switch contacts during normal starting.
If loss is in excess of 0.2 volts per 100 amperes, the solenoid should be replaced.
c. If solenoid fails to operate when the manual is turned on or if it fails to
release
when the manual switch is released, it should be removed and tested to
specifications. If either
opening or closing voltages are not specified, replace
the solenoid.
Reissued: 10/12/79
ELECTRICAL SYSTEM
4C23