Piper SEMINOLE PA-44-180, Maintenance Manual

Page: 136 / 881

A. Disconnect the primary wire from the primary terminal of the ignition assembly.
B. Carefully unscrew and disconnect the high voltage ignition cable at the spark plug. Exercise care to
avoid fouling or damaging the connector.
C. Remove the four attaching screws and lift the ignition assembly off the heater jacket.
2. Installation: (Refer to Figure 21-18.)
A. Place the ignition assembly in position on the heater jacket with the high voltage cable facing the
spark plug end of the heater.
B. Install the four screws. Tighten the screws securely.
C. Carefully connect the high voltage lead to the spark plug.
D. Connect the primary lead to the primary terminal on the ignition unit and tighten the nut securely.
E. Check for proper heater operation.
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:
1. A battery that will supply power at approximately 14 volts DC.
2. A voltmeter with a range of 0-15 volts.
3. 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.
— CAUTION —
WHEN TESTING AN IGNITION UNIT, DO NOT USE A SCREWDRIVER AS
A SUBSTITUTE FOR A SPARK PLUG AND SPARK PLUG FIXTURE.
4. A spark gap of 0.187 inch (plus 0, minus .030). 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 21-10 for information on fabricating this fixture)
— Note —
Any one of several spark plugs may be used with the spark plug fixture detailed in
Figure 21-10. 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.
5. The high tension shielded ignition lead between the ignition unit and the spark plug is a part of the cover
assembly.
6. Arrange the test equipment as shown in Figure 21-11.
OPERATIONAL TEST OF IGNITION UNIT.
1. Close the momentary switch and read the voltmeter and ammeter. Release the momentary switch
immediately.
2. The amperage reading at 14 volts DC must be 1.50 +/- 0.25 amperes.
PA - 4 4 - 1 8 0 / 1 8 0 T
AIRPLANE MAINTENANCE MANUAL
2 1 - 4 3 - 1 6
Page 21-25
Revised: May 15, 1989
1F16
PIPER AIRCRAFT