TROUBLESHOOTING PROCEDURES - TM-10-3930-644-14-P0253

TM 10-3930-644-14 & P

C. TROUBLESHOOTING PROCEDURES

1. Undercharged Battery

Close adherence to the following procedures in the order

This condition, as evidenced by slow cranking

presented will lead to the locations of charging system

and low specific gravity readings, can be caused

defects in the shortest possible time. Only a portion of

by one or more of the following conditions, even

those procedures need be performed. It will never be

though the ammeter may be operating normally.

necessary to perform all the procedures in order to

locate the trouble.

a. Insure that the undercharged condition

has' not been caused by accessories

A basic wiring diagram showing lead connections is

having been left on for extended periods.

shown in Figure 2-4. To avoid damage to the electrical

equipment, always observe the following precautions:

b. Check the drive belt for proper tension.

1. Do not polarize the alternator.

c. If a battery defect is suspected, check the

battery as described in the Battery Service

2. Do not short across or ground any of the

section.

terminals in the charging circuit except as

specifically instructed herein.

d. Inspect the wiring for defects. Check all

connections for tightness and cleanliness,

3. NEVER operate the alternator with the output

including the slip connectors at the

terminal open-circuited.

alternator and firewall, and the cable

clamps and battery posts.

4. Make sure the alternator and battery have the

same ground polarity.

e. With ignition on and all wiring harness

leads connected, connect a voltmeter

5. When connecting a charger or a booster battery

from:

to the vehicle battery, connect negative to

negative and positive to positive.

alternator "BAT" terminal to ground,

Trouble in the charging system will shot up as one or

alternator No. 1 terminal to ground, and

more of the following conditions:

alternator No. 2 terminal to ground.

1. Faulty ammeter operation.

A zero reading indicates an open between

2. An undercharged battery as evidenced by slow

voltmeter connection and battery. The

cranking and low specific gravity readings.

alternator has , built-in feature which

avoids overcharge and accessory damage

3. An overcharged battery

evidenced

by preventing the alternator from turning

excessive water usage.

on if there is an open in the wiring harness

connected to the No. 2 terminal. Opens in

the wiring harness connected between-the

No. 2 terminal and battery may be

between the terminals, at the crimp

between the harness wire and terminal, or

in the wire.

f. If previous Steps a. through e. check

satisfactorily, check the alternator as

follows:

(1) Disconnect battery ground cable.

(2) Connect an ammeter in the circuit at

the "BAT" terminal of

Figure 2-4. Alternator Typical Wiring Diagram

R-146-1

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