Testing (Heater And Ventilating System) - Piper Navajo Chieftain PA-31-350 Service Manual

NAVAJO CHIEFTAIN SERVICE MANUAL
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.
NOTE
The nozzle (23) can be spray tested by installing it in the holder
and connecting the fuel tube to a 7 psi fuel pressure source. The
conical angle spray pattern should be even and dispersed the same
in all directions. Exercise caution to keep atomized fuel away
from fire.
k. Inspect the nozzle holder for damaged threads at the fuel-tube fitting and for crimped or cracked
fuel line or distorted housing. Check the solenoid for continuity by connecting across each wire lead with
an ohmmeter. A reading of between 100 and 125 ohms should be obtained at room temperature. If not
within these limits, it should be replaced.
1. Remove the brushes, one at a time, from the ventilating air blower motor (30) by removing the
brush cap and carefully withdrawing the brush from its guide. Remove foreign material from the brush
guide and commutator with a stream of filtered compressed air. Check for brush wear. (Refer to Paragraph
13-25.) Inspect the commutator for grooved brush track, pitting or burning. The commutator surface
should be smooth and medium brown in color. Replace the motor if the commutator or other parts show
damage.
m. Inspect the combustion air blower motor as described in the preceding step.
n. Inspect the blower fan for broken or bent blades and replace it for either condition.
13-43. TESTING. The following tests should be performed as outlined in the succeeding paragraphs.
a. Check ventilating air and combustion air motors for correct RPM and current draw.
1. Connect motor to 28-volt DC power supply. Rotation should be counterclockwise when
viewed from the shaft end.
2. Both motors should rotate at approximately 7500 RPM at rated voltage. Current draw is
approximately three amperes.
3. If current draw is excessive, or if speed is too low, replace the brushes. Recheck both
current draw and RPM after brushes are properly run-in. (Refer to Paragraph 13-25, b.)
4. If after replacing brushes operation is still unsatisfactory, replace the motor.
NOTE
The motor checks described above should be made without the
blower housing attached, for both the ventilating
air and
combustion air motors.
b. Test the combustion tube assembly (20) for leaks as follows:
1. Fashion a sealing plate from approximately .125 inch thick flat stock to seal the combustion
head opening in the combustion tube assembly. (Refer to Figure 13-14.) Use a rubber gasket under the plate
and attach the plate with two screws.
2. Make up seals for all remaining openings, except the one used to connect the air pressure source.
(Refer to Figure 13-14.) Use rubber stoppers as shown. The combustion air inlet tube can be sealed best with a
drilled stopper and clamp. Other openings should be sealed with expansion plugs. The seal used in the exhaust
tube should be formed so that it will not deform the air pressure switch tube which protrudes into the exhaust.
Reissued: 9/23/80
HEATING AND VENTILATING SYSTEM
4 C11