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