Dc Electrical System; Description; Alternator Troubleshooting; Checking For Propcr Voltage - Universal M3-20A Operator's Manual

DC ELECTRICAL SYSTEM
DESCRIPTION
The charging system consists of an alternator with a mounted
voltage regulator, an engine DC wiring harness, a mounted
DC circuil breaker, and a battery and connection wires.
Because of the use of integrated circuits (Ie's) the electronic
voltage regulator is very compact and is mounted internally
or on the back of the alternator.
Alternator Troubleshooting
If you suspect that the alternator is not producing enough
voltage to charge the engine's battery, check the following:
A
WARNING:
A failed alternator can becDme very
hDt. Do nDt touch until the alternator has cODled dDwn.
o
Make certain your alternator is securely mounted.
o
Check the drive belts for proper tension.
o
Inspect for loose or disconnected wires at the alternator.
NOTE:
An isolator with a diode, a solenoid, or a battery
selector switch is usually mounted in the circuit to isolate the
balleries so the starting ballery is not discharged along with
the house batteries. If the isolator is charging the slarling
ballery but not the house ballery, the alternator is OK and
the problem is in the ballery charging circuit.
A
WARNING:
Shut Dff the engine battery switch Dr
discDnnect from the battery when wDrking Dn the engine
electrical system.
Checking for Proper Voltage
If you suspect the alternator has failed perform the following
tests with the engine off:
1. Using a voltmeter, connect the voltmeter red wire clip to
the output terminal B+.
2. Connect the voltmeter negative wire to any ground on the
engine.
3. Check the battery voltage. It should read 12 to 12 volts.
4. Check the voltage between the alternator (+) positive
ter~
minai B and any engine ground. If the circuit is good, the
voltage at the alternator should be the same as the battery
(unless there's an isolator in the circuit, then the reading
would be zero).
A
CAUTION:
TD aVDid damage tD the battery charging
circuit, never shut Dff the engine battery SWitch when
the engine is running!
20
A
WARNING:
Before starting the engine make certain
that everyone is clear Df mDving parts! Keep away frDm
sheaves and belts during
test
prDcedures.
.
5. Start the engine.
6. The voltage reading for a properly operating alternator
should be between 13.5 and 14.5 volts. If your alternator
is over- or undercharging, have it repaired at a reliable
service shop.
NOTE:
Before removing the alternator for repair, use your
voltmeter
to
ensure that 12 volts DC "excitation is preselll at
the R terminal if the previous lest showed ollly ballery volt-
age at the B output terminal.
.14 PINK!1IlUE
'14 PINK/8LUE
.1U RED
==!t:::<l(5l:'5,
TYPICAL UNIVERSAL 51 AMP
ALTERNATOR CONNECTIONS
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'14 PINKIBLUE
L __
JOI~~~==-
814 BROWN
OPTIONAL 72 AMP
ALTERNATOR CONNECTIONS