If no voltage was indicated while testing fuel solenoid lead terminal 421,
test terminal B of the main wiring harness at the APU wall mount by placing
the red multimeter probe on wall-mounted connector terminal B and the black
probe to ground.
Set the MASTER and FUEL SHUT OFF switches to the ON
position. If voltage is indicated, harness lead 421 from the wall-mounted
connector to the fuel solenoid requires repair or replacement.
Figure 14 when performing this test.
APU Wall Mount Main Harness Connector B.
If no voltage is indicated during the test of terminal B, reconnect the main
harness connector. Set the MASTER switch to the OFF position and remove the
APU control box and disconnect the plug from the control box. Now make a
voltage check by connecting the red multimeter probe on harness connector
terminal socket N and the black probe to a good ground.
Set the MASTER
switch to the ON position.
If no voltage is indicated, the main cargo
compartment harness lead 419 is defective and you must notify support
maintenance. Refer to Figure 15 when performing this test.
If voltage was present when testing terminal N, set the MASTER switch to the
OFF position. A test of the APU control box FUEL SHUT OFF switch circuitry
is now necessary. Place the multimeter red probe on control box receptacle
terminal pin N, and place the black probe on terminal pin F. Set the FUEL
SHUT OFF switch to ON.
The meter should indicate 0 ohms.
If the meter
remains on infinity with the switch on, then a continuity check of the panel
the item found to be defective.
Refer to Figure 16 when performing this