Inspection Of Remaining Components - Piper Navajo Chieftain PA-31-350 Service Manual

NAVAJO CHIEFTAIN SERVICE MANUAL
through the combustion tube assembly and sighting along the outer surface of the inner combustion tube.
An assembly that has been obviously deformed should be replaced. Slight deformation will not affect
heater operation unless it is extensive and localized enough to reduce the flow of ventilating air through the
heater more than 10 percent. Inspect the sensing tube for clogging. If it is clogged. it must be cleaned
Disconnect at switch and clear 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.
c.
The combustion tube assembly may be cleaned by either of two methods:
I.
One method is to soak the combustion tube assembly overnight in a solution of Kelite No.
1.235 cleaning solution. (I to 12 parts by volume). The solution should be maintained at a temperature of
between 190°F and 210
°
F. After overnight soaking. rinse the combustion tube assembly thoroughly in water
to remove all traces of the Kelite solution. In order to reach all areas of the combustion tube assembly. it is
advisable to let it stand in the rinsing water for as long as 1 2 hour. while occasionally agitating it to circulate
the water. All openings should be left open duringthis operation. Besure to drythecombustion
tube assembly
thoroughly after cleaning by blowing with air.
2.
A second method of cleaning is what is commonly known as hand "tumbling". Insert shot
or glass beads 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.
13-42. INSPECTION OF REMAINING COMPONENTS.
(Refer to Figure 13-17.)
a.
Discard all rubber parts such as grommets, gaskets, etc. These items should always be replaced at
overhaul. Also discard the rope gasket (21).
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 lockwashers. Replace
damaged parts.
d.
The combustion air pressure switch (17) installed on the system must respond to delicate pressure
changes and should always be checked and/or replaced at overhaul. (Refer to paragraph 13-43, c and Figure
13-15.)
e.
Replace the vibrator in the ignition unit at each overhaul.
f. Inspect the ignition assembly (4) (Figure 13-17) 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 (10) 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 (23) 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
Revised: 10/15/82
HEATING AND VENTILATING SYSTEM
4C10