Test Setup For Combustion Air Pressure Switch - Piper Navajo PA-31 Service Manual

1. WATER
MANOMETER
2. OHMMETER
3. NEEDLE VALVE
4. TEE
5. PRESSURE TAP (OPEN)
6. ADJUSTING SCREW
7. COMBUSTION
AIR PRESSURE
SWITCH
Figure 13-25. Test Setup for Combustion Air Pressure Switch
4.
Make several trials to insure switch reliability. Be sure to increase and
decrease the air
pressure slowly in order to produce accurate indications.
5. If an adjustment is required, rotate the adjusting screw clockwise to increase
settings and
counterclockwise to decrease settings.
^
d.
Test the combustion
air
blower switch as follows when installed with
heater
1.
Connect an adjustable air pressure line that can be controlled in
a range of zero to 10.0
inches (maximum) of water to the switch opening with a water manometer
and needle valve in the line
ahead of the switch. Switch must be tested in the same position as installed
in the airplane. (Refer to Figure
13-26.)
2. Connect an ohmmeter across the switch terminals to determine the exact
instant of switch
opening.
3.
Apply air pressure, slowly allowing it to build up from zero. The switch
contacts should
open at 5.0± 0.3 inches of water which will indicate on the manometer and
close at 2.5 inches.
NOTE
The switch has a differential pressure tap and this opening must be
left open to atmosphere during the test.
4. Make several trials to insure switch reliability. Be sure to increase and
decrease the air
pressure slowly in order to produce accurate indications.
5.
If an adjustment is required, rotate the adjusting screw clockwise
to increase and
counterclockwise to decrease settings.
e. Test the fuel feed and nozzle holder assembly for leaks as follows: This test can be simplified if
the following routine is used to test both the fuel line and fuel line shroud tube.
1.
Using filtered compressed air, apply 20 psi to the shroud drain port, located
on the surface
near the threaded nozzle cavity.
Reissued: 10/12/79
HEATING AND VENTILATING SYSTEM
PIPER NAVAJO SERVICE MANUAL
5C15