TM-9-2350-311-20-2

HOWITZER, MEDIUM, SELF-PROPELLED, 155MM; M109A2, M109A3, M109A4 AND M109A5

TECHNICAL MANUAL; UNIT MAINTENANCE MANUAL FOR CAB, ARMAMENT, SIGHTING AND FIRE CONTROL, ELEVATING AND TRAVERSING SYSTEMS AND ASSOCIATED COMPONENTS

DECEMBER 1993

  TM-9-2350-311-20-2 - Page 202 of 828

TM 9–2350–311–20–2
3–90
Change 2
3–3
TROUBLESHOOTING
— CONTINUED
h.
CAB LIGHTING SYSTEM
— CONTINUED
(1)
ONE OR MORE DOME LIGHTS ARE OUT,
BUT SIGHTING EQUIPMENT LIGHTS OPER-
ATE.
— CONTINUED
1.
Turn MASTER switch to OFF.
2.
Remove incandescent lamp from failed socket
assembly.
3.
Place red multimeter lead on contact in center of
socket and black lead to ground.
4.
Turn MASTER switch to ON.
5.
Turn dome light switch to the position of the
failed socket assembly.
6.
Check for voltage.
Is battery voltage present?
1.
Turn MASTER switch to OFF.
2.
Reconnect wire 138 to dome light assembly if
disconnected.
3.
Remove cover from faulty dome light assembly
(para 8–11).
4.
Turn MASTER switch to ON.
NOTE
Dome light assembly switch must be placed in position
B for blue (blackout) light output terminal “R”, then
position C for white light output terminal “W”.
5.
Place red multimeter lead to dome light
assembly switch output terminals (R, then W)
and black lead to ground.
6.
Check for voltage.
Is battery voltage present in both positions?
yes
no
C
CONTINUED FROM STEP A OR B
Replace dome light
assembly switch
(para 8–11 ).
END OF TASK
yes
no
D
Repair or replace dome
light assembly (para 8–11).
Replace incandescent
lamp (para 8–11 ).
OUTPUT TERMINALS R AND W
+
DOME LIGHT
ASSEMBLY
SWITCH


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