TM 9-2330-381-14
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
APU - CONT
Step 3.
With APU control box cover removed (para. 4-32), tag and
disconnect four leads (red, red, white, and blue) from bridge
rectifier. Check conductivity across diodes within rectifier
with an electrical tester (multimeter) (item 17, appx. B) set
on lowest resistance setting. Probe four bridge rectifier
leads as follows:
Negative Lead
Positive Lead
Results
Red (both leads)
White
Nonconductive
White
Red (both leads)
Conductive
Blue
Red (both leads)
Nonconductive
Red (both leads)
Blue
Conductive
If actual readings are different than specified above, remove
and replace bridge rectifier (para. 4-108).
14.
GLOW PLUG HEATS SLOWLY OR FAILS TO HEAT
Step 1.
Check for discharged or defective battery (para. 4-10, item 5).
Charge or replace battery (para. 4-30).
NOTE
On APU with APU engine serial number 504697 and subsequent, the glow plug
indicator is changed from glow-type indicator to lamp driven by a timer.
Step 2.1
For glow-type glow plug indicator, hold starter switch in GLOW
position and observe glow plug indicator element (para. 2-2).
If glow plug indicator element fails to glow within 29 seconds,
remove wire from glow plug and hold wire terminal to APU frame
to ground that wire.
a. If element fails to glow, replace APU control box glow plug
indicator (para. 4-108).
b. If element glows, replace glow plug (para. 4-97).
Change 2 4-30.1/(4-30.2 blank)
