Section V. M42 ALARM UNIT

TM 3-6665-225-12

(1) Release four catches (12, fig. 1-2) from

(4) Center bail (2) on bottom of detector cell (3)

catches (13) and separate detector assembly (6)

and turn lobed nut clockwise until fingertight.

from bottom case assembly (9).

(5) Replace detector assembly (6, fig. 1-2) in

(2) Release two catches (5, fig. 3-22) on pump

bottom case assembly (9) and secure four catches

assembly (6).

(12).

(3) If necessary, rock pump assembly (6)

3-13. Electronic Module

slightly while pulling it directly away from chassis

assembly (1).

a. Removal.

(4) Record pump assembly operating hours

(1) Release four catches (12, fig. 1-2) from

since last tubing replacement on modified DA Form

catches (13) and separate detector assembly (6)

2408-1 (para 2-20).

from bottom case assembly (9).

(2) Rotate turnlock fastener (4, fig. 3-22) fully

b. Replacement.

(1) Dampen outside of the four ports on top of

counterclockwise and pull electronic module (7)

pump assembly (6) with water.

from its housing on chassis assembly (1).

(2) Position pump assembly (6) so that its elec-

b. Replacement.

(1) Position electronic module (7) so that its

trical connector and ports are alined with their re-

ceptacles in chassis assembly (1).

electrical connector will mate with electrical con-

(3) Press pump assembly (6) into place in chas-

nector in chassis assembly (1).

sis. Secure pump assembly in position with two

(2) Slide electronic module (7) into housing on

catches (5).

chassis assembly (1).

(4) Replace detector assembly (6, fig. 1-2) in

(3) Push turnlock fastener (4) toward chassis

bottom case assembly (9) and secure four catches

assembly (1). Rotate turnlock fastener clockwise

(12).

until its tip touches housing and electronic module

(5) Enter the hours when next pump assembly

(7) is secured in position.

replacement is due on M43 daily log (para 2-19).

(4) Replace detector assembly (6, fig. 1-2) in

bottom case assembly (9) and secure four catches

(12).

3-14. Pump Assembly

a. Removal.

Section V. M42 ALARM UNIT

3-15. General

CAUTION

Observe battery polarity as shown on label

The operator is authorized to replace batteries in

inside battery retainer.

the M42 alarm unit.

(1) Install four BA3030 batteries in battery re-

3-16. Batteries

tainer (9), close hinged cover, and secure it with

spring-tension clip (8).

a. Removal.

(2) With gasket (10) in place, position chassis

(1) Position selector switch (6, fig. 3-23) to

assembly (4) in housing (5).

HORN OFF.

(3) Secure by tightening four knurled screws

(2) Loosen four knurled screws (2) and separate

(2).

chassis assembly (4) from housing (5).

c. Test.

(3) Release spring-tension clip (8) and open

(1) Position selector switch (6) to TEST. Loud-

hinged cover of the battery retainer (9).

speaker (3) will sound and ALARM-RED indicator

(4) Remove batteries (7) from battery retainer

(1) will flash.

(9).

(2) Set selector switch (6) to HORN OFF.

b. Replacement.

Change 2

3-25