Piper Navajo PA-31 Service Manual page 942

PIPER NAVAJO SERVICE MANUAL
2.
A second method of cleaning is what is commonly known as hand "tumbling."
Insert shot
or other metallic particles through the exhaust outlet opening; then close all openings
and shake the
combustion tube assembly vigorously, while rotating it and changing from
end-to-end frequently. Be sure to
pour out all of the particles and loosened material; then with all openings
uncovered, direct a stream of
compressed air into the combustion tube assembly from first one opening;
then the other. Make sure all
loose material is removed. Inspect the sensing tube for clogging. If it is
clogged, it must be cleaned.
Disconnect at the switch and clear the tube by blowing air through it. If combustion
product residue has
collected in the exhaust end of the tube, it may be necessary to clear the tube with a wire.
13-44. INSPECTION OF REMAINING COMPONENTS. (Refer to Figure
13-27, 13-28 or 13-29.)
a.
Discard all rubber parts such as grommets, gaskets, etc. These items should
always be replaced at
overhaul. Also discard the rope gasket.
b. Inspect all wires and wiring harnesses for damage to insulation, damaged
terminals, chafed or
cracked insulation and broken plastic bands. Individual wires can be replaced by
making up new wires from
No. 16 AWG stock and cut to correct length. It is advisable to use an acceptable
crimping tool for installing
terminals, rather than solder for all heater wiring connections. If wiring harness
damage is visible, the entire
harness assembly should be replaced. If only one or more wires are damaged,
cut the cable ties, make up
new wires, install them in the harness, and restore all cable ties and clamps.
If heater controls were
operating properly at the time of removal, reinstall them.
c. Inspect all hard parts, consisting of bolts, screws, nuts, washers and lock
washers. Replace
damaged parts.
d.
The combustion air pressure switch and the combustion air blower switch
installed on later
systems must respond to delicate pressure changes and should always be checked
and/or replaced at
overhaul. (Refer to Paragraph 13-45, Steps c and d, and Figure 13-25 or 13-26.)
e. Replace the vibrator in the ignition unit at each overhaul.
f. Inspect the ignition assembly for dented case, loose or damaged primary terminal
insulator and
broken or obviously damaged high-voltage lead. Give particular attention to the
condition of the spring
connector at the end of the lead. If the spring is burned off, visibly eroded, or
carbon tracked, the ignition
assembly should be replaced.
NOTE
Do not attempt a field repair of the ignition unit, as it is a sealed
assembly.
g.
Inspect the terminal strip for distortion and cracks and replace it if either condition
exists.
h. Inspect radio-noise filters for short circuits by checking from either terminal to ground with an
ohmmeter. An open-circuit reading should be obtained.
i.
Inspect the spray nozzle with a magnifying glass for any obstructions in
the nozzle orifice and
any sign of damage to the slight conical protrusion at the nozzle tip.
Use compressed air to remove
obstructions and re-examine the orifice to make sure it is open. Exercise
care when handling the nozzle to
avoid pressing or rapping on the tip face. Do not burr or scrape off deposits on the tip face. After cleaning,
it is advisable to store the nozzle in a polyethylene bag until ready for reassembly.
j.
Replace the nozzle at overhaul.
Reissued: 10/12/79
HEATING AND VENTILATING SYSTEM
5C12