3.
Troubleshooting the APU Air Intake System.
This portion of the subcourse pertains to troubleshooting the APU engine air
intake system as a result of the engine overheating during normal operation.
However, prior to troubleshooting the APU air intake system, make the
following preliminary checks:
o
Check that all air intake ducts and passages are free of
obstructions.
Clean or replace the air cleaner filter element
(paragraph 1, Part C, this subcourse).
o
Open the front APU access door and unscrew and remove the oil
dipstick.
Wipe the dipstick with a clean rag and reinsert and
withdraw the dipstick.
If oil level is below the full mark,
remove the oil filler cap and add oil until oil comes up to the
"F" mark on the oil dipstick (Figure 19).
Be sure to use the
grade of oil specified in Lubrication Order 9-2350-267-12.
If after completing the preliminary steps referenced above and in Part C of
this subcourse, the HIGH AIR TEMPerature light remains lit when the engine
is cool, use the following procedures to determine the cause of the APU
engine overheating:
Figure 19.
APU Air Ducts and Oil Level Indicator.
o
Disconnect lead 493 from the high temperature switch of the APU.
If the HIGH AIR TEMPerature light goes out, the high air
temperature switch is defective. Notify the Support Maintenance
activity when the switch is defective. If the light remains on
after removing lead 493, perform the next following step (Figure
20).
19
OD1702
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