TM 1-1520-238-T-5
7–143
7–49.
SHAFT DRIVEN COMP INDICATOR – REMAINS LIGHTED AFTER APU START CYCLE (cont)
7–49
7. Check SDC overboard vent for very strong,
steady air discharge.
Is very strong, steady air discharge present?
YES
Replace SDC total pressure
sense line filter and surge valve
pressure filter
(TM 1-1520-238-23).
If filters have been replaced
once, replace SDC assembly
(TM 1-1520-238-23).
NO
Replace SDC inlet throttle valve
(TM 1-1520-238-23).
8. Shutdown APU (TM 1-1520-238-23).
(AAG) Check for open between P217–2 and
GS541–F.
(ABC) Check for open between P217–2 and
GS543–F.
Does open exist?
YES
Repair open wire.
Go to paragraph 7–45.
NO
Go to step 9.
9. Check for open between (A402)J1–48 and
P217–1.
Does open exist?
YES
Go to step 10.
NO
Refer to TM 1-1520-238-T-6 to
troubleshoot circuit protection
system (dc emergency bus –
pilot station).
10. Check for open between (A402):
K2–1/2–A3 and K2–1/2–A2.
Does open exist?
YES
Replace relay (A402)K2–1/2.
(TM 1-1520-238-23).
NO
Repair open wire between:
P442–B3 and P217–1.
(A402):
J1–48 and TB2–6–D,
XK2–1/2–A3 and J5–B3,
TB2–6–B and XK2–1/2–A2.
Go to paragraph 7–45.
11. With APU running and air flowing from ECS
vents, detach wire from GS541–K.
Is SHAFT DRIVEN COMP indicator on?
YES
Go to step 12.
NO
Replace SDC outlet pressure
switch (TM 1-1520-238-23).
12. Check for short to ground between:
P440–B15 and P18–38,
P442–B1 and P1323–3.
(A402):
J5–B1 and TB2–12–S,
TB2–12–R and J16–B15.
Does short exist?
YES
Repair shorted wire.
Go to paragraph 7–45.
NO
Replace pilot caution/warning
panel (TM 1-1520-238-23).
END OF TASK
