SECTION XIII. ELECTRICAL SYSTEM INSTRUMENTS AND GAGES

Custom Search

Figure 4-37. Engine water manifold removal

TM-55-1905-217-12 Landing Craft Mechanized; Steel; DED; Overait Length 74 Feet Mod 1 Marl VIII Navy Design LCM-8 Hull Numbers 8500 and 8580 thru 8618 Manual

Figure 4-41.1. Alternator testing.(Sheet 1 of 8)

TM 55-1905-217-12

Figure 4-39. Fresh water pump mounting.

Figure 4-40. Raw (sea) water pump mountings.

SECTION XIII. ELECTRICAL SYSTEM INSTRUMENTS AND GAGES

b. In-Vessel Testing (Hull numbers 8500 thru 8519

4-47.

General

and 8520 thru 8539). The following test procedures may

be performed to determine the condition of the alternator

The electrical system (1-3 and 1-4 )includes two 70-amp,

and regulator while still in the vessel.

24-volt alternators, one alternator mounted on the

inboard engine of each propulsion unit. Four 6-volt

batteries, connected in series to provide 24-volt current,

NOTE

are contained in the battery box located aft in the engine

room. The alternators and batteries provided electrical

When making the alternator system test, the batteries

power to operate all lights and electrical accessories on

must be in good condition and fully charged.

the landing craft and for the electric starters which are

mounted on the outboard engines of each propulsion

CAUTION

unit.

Do not under any circumstances, short FIELD terminal of

4-48.

Alternators

alternator to ground. Do not disconnect regulator while

alternator is operating. Do not disconnect alternator

a. Description. One 70-amp, 24-volt alternator is

output lead from alternator while the alternator is

belt driven from the inboard engine crank-shaft pulley.

operating.

The electrical circuit of the alternator uses six silicon

diodes in a full wave rectifier circuit. Since the diodes will

(1) Check voltage across auxiliary terminal

(fig. 4-41.1) and negative output terminal with dc

pass current from the alternator to the battery or load but

will not pass current from the battery to the alternator, the

voltmeter. Correct voltage is 0.2 volt. If the voltage

alternator does not require the use of cutout relay. A

exceeds this value, the isolation diode is defective (fig.

voltage regulator is the only control required.

4-41.3).

(2) Place jumper wire across oil pressure

switch on propulsion unit to short out switch. Check

CAUTION

voltage across auxiliary terminal (fig. 4-41.1) and

negative output terminal with dc voltmeter. Correct

Disconnect battery cables when working on alternator or

voltage is 1.8-to 2.5-volts. This test evaluates field

regulator.

circuit. If voltage at

4-43