Piper Navajo PA-31 Service Manual page 943

PIPER NAVAJO SERVICE MANUAL
NOTE
The nozzle can be spray tested by installing it in the holder and
connecting the fuel tube to a 7 psi fuel pressure source. On nozzle
holder with solenoid valve per Figure 13-27 or 13-28 connect the
solenoid leads to a 24-volt battery to open the solenoid valve. 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 and solenoid valve assembly 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 78 and
82 ohms for solenoids installed on
39D59 heaters or 100 to 125 ohms for solenoids installed on B39D59 heaters
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
(44) 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
13-26.) 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 wheel for broken or bent vanes and replace it for either
condition.
13-45. TESTING. The following tests should be performed as outlined in the
suceeding 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
13-26, Step 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 (19) for leaks as follows:
1.
Fashion a sealing plate from approximately .125 inch thick flat stock to
seal the nozzle
holder or combustion head opening in the combustion tube assembly. (Refer
to Figure 13-24.) Use a rubber
gasket under the plate and attach the plate with screws.
2. Make up seals for all remaining openings, except the one used to connect
the air pressure
source. (Refer to Figure 13-24.) 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: 10/12/79
HEATING AND VENTILATING SYSTEM
5C13