Piper Navajo PA-31 Service Manual page 934

PIPER NAVAJO SERVICE MANUAL
NOTE
The dimension "A" in Figure 13-21 must be varied with the length
of spark plug electrode to provide a gap of 0.156 to 0.188 for
39D18 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 13-22.
13-31. OPERATIONAL TEST OF IGNITION UNIT.
a. Close the momentary switch and read the voltmeter and ammeter. Release the momentary switch
immediately.
b. The amperage reading at 28-volts D.C. must be 1.25 ±0.25 amperes.
13-32. VIBRATOR. The vibrators should be replaced after 250 hours of operation. This schedule applies
equally to vibrators installed in new units as well as new vibrators installed in ignition units that have been
in service.
13-33. VIBRATOR REMOVAL AND INSTALLATION. (Refer to Figure 13-15.)
a.
Remove the clamp from the housing brackets that secure the vibrator.
b.
Remove the vibrator 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 entering the pin sockets in the vibrator socket; then press the vibrator fully and firmly into position.
d. Replace the clamp.
13-34. LIMIT (OVERHEAT SAFETY) SWITCH AND CYCLING SWITCH. (Refer to Figure 13-27, 13-28
or 13-29.)
a. Removal:
1. If the limit switch is damaged or defective, disconnect the two electrical leads from the
switch terminals. Be sure to mark the leads for proper reassembly. (The switch terminals are identified by
numbers "1," "2" and "3.")
2. Remove the two attaching screws and lift the limit switch and spacers (gaskets) from the
jacket opening.
3. If the cycling switch (9) is damaged or defective, disconnect the electrical leads, being sure
to mark them for proper reassembly.
4. Remove the two screws and lift the cycling switch from the jacket opening.
NOTE
No attempt should be made to repair either of these switches. If
they do not operate properly, they should be replaced. (Refer to
Paragraph 13-52, m and n for test instructions.)
Reissued: 10/12/79
HEATING AND VENTILATING SYSTEM
5C4