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 249 of 828

TM 9–2350–311–20–2

3–137

j.

NBC SYSTEM CIRCUIT — CONTINUED

(7)

NBC CONTROL BOX ASSEMBLY INDICATOR

LIGHT ILLUMINATES, BUT ASSISTANT GUN-

NER’S M3 ELECTRICAL HEATER DOES NOT

OPERATE.

INITIAL SETUP

Applicable Configuration

M109A4/M109A5 howitzers

Test Equipment

Multimeter (item 6, Appx H)

Tools

Artillery and turret mechanic’s tool kit

(SC 5180–95–CL–A12)

Equipment Condition

Vehicle MASTER switch to OFF (TM 9–2350–311–10)

CAB NBC POWER switch to OFF (TM 9–2350–311–10)

1.

Disconnect wire 136C from assistant gunner’s

M3 electrical heater.

2.

Turn MASTER and CAB NBC POWER

switches to ON.

3.

Place red multimeter lead in wire 136C and

black multimeter lead to ground.

4.

Check for voltage.

Is battery voltage present?

yes

no

A

Replace M3 electrical

air heater (para 17–2).

B

CONTINUED ON NEXT PAGE

–

+

ASSISTANT

GUNNER’S

HEATER

WIRE 136C

–+

1.

Turn MASTER and CAB NBC POWER switches

to OFF.

2.

Disconnect NBC power lead assembly at J2

connector on NBC control box assembly.

3.

Place one multimeter lead in wire 136C and

other lead to pin C of NBC power lead assembly

connector.

4.

Check for continuity.

Is continuity present?

WIRE 136C

NBC POWER LEAD

ASSEMBLY CONNECTOR

PIN C