Testing Ignition Unit; Operational Test Of Ignition Unit; Vibrator Removal And Installation - Piper Navajo Chieftain PA-31-350 Service Manual

NAVAJO CHIEFTAIN SERVICE MANUAL
13-29. TESTING IGNITION UNIT. The ignition unit does not require complete overhaul. The following
test will indicate whether or not the unit is operational and whether the vibrator should be replaced before
reinstallation in the aircraft. The following equipment is required to test the components:
a.
A battery that will supply power at approximately 24-volts DC.
b.
A voltmeter with a range of 0-30-volts.
c.
A lead from the battery to the test fixture in which is included an ammeter with a range of 0-3
amperes and a normally open. momentary-closed switch. The total resistance of the lead including the
ammeter and switch must not exceed 0.3 ohms.
d.
A spark gap of 0.187 inch ± 0. A convenient means of arranging the correct spark gap is to install
a spark plug. P N 39D18. in a test fixture arranged to provide a ground electrode and a .187 inch spark gap.
(Refer to Figure 13-9 for information on fabricating this fixture.)
NOTE
Any one of several spark plugs may be used with the spark plug
fixture detailed in Figure 13-9. However, the "A"dimension in that
sketch must be varied with the length of spark plug electrode to
provide a gap of .187 inch for all spark plugs.
CAUTION
When testing an ignition unit. do not use a screwdriver as a
substitute for a spark plug and spark plug fixture.
e.
The high tension shielded ignition lead between the ignition unit and the spark plug is a part of
the cover assembly.
f.
Arrange the test equipment as shown in Figure 13-10.
13-30. OPERATIONAL
TEST OF IGNITION UNIT.
a.
Close the momentary switch and read the oltmeter and ammeter. Release the momentary switch
immediately.
b.
The amperage reading at 28 volts D.C. must be 1.25 ± 0.25 amperes.
13-31. VIBRATOR. The vibrators should be replaced after 250 hours of operation. This schedule applies
equally to ibrators installed in new units as well as new vibrators installed in ignition units that have been
in ser ice.
13-32. VIBRATOR REMOVAL AND INSTALLATION.
(Refer to Figure 13-17.)
a.
Remove the hose type clamp from the housing brackets that secure the vibrator.
b.
Remove the vibrator (3) from the ignition unit: it may require a slight back and forth movement.
to remove it from the unit. A piece of masking or friction tape around the exposed portion of the vibrator
will help to grip the vibrator for removal.
c.
Install the new vibrator with the index marks aligned. The connector pins on the vibrator can be
felt enterng the pin sockets in the vibrator socket: then press the vibrator fully and firmly into position.
d. Replace the clamp.
Revised: 10/15/82
4C2
HEATING AND VENTILATING SYSTEM
4C2
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