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ON VEHICLE TROUBLESHOOTING GUIDE
ALTERNATOR ELECTRICAL CONDITION - Low Voltage - High Voltage - No Voltage
PRELIMINARY PROCEDURES
Common problems, all applications:
Check alternator drive belt (s).
Check alternator positive connection
Check alternator ground connection
on alternator.
Check condition of connector between regulator
and alternator.
Identify model of alternator_______________
Identify model of regulator________________
Record voltage regulator set points
stated on regulator tag:
1)_______ 2)_______ 3)_______ (if applicable)
LOW VOLTAGE OUTPUT
Causes of low voltage:
Loose drive belt.
Low state of charge of battery.
Current load on system greater than alternator
can produce.
Defective wiring or poor ground path.
Low regulator set point.
Defective voltage regulator.
Defective alternator.
HIGH VOLTAGE OUTPUT
Causes of high voltage:
Wrong regulator.
High regulator set point.
Defective regulator.
Defective alternator.
M13002 2/99
SELF ENERGIZED ALTERNATOR
24VDC Electric Supply System
with 220 Amp. Niehoff Alternator
NO VOLTAGE OUTPUT
Causes of no voltage output:
No drive belt.
No battery (B+) voltage at alternator's "B+" termi-
nal (except isolator type systems).
No "link" from "R" terminal to energize ("E") ter-
minal on alternator when engine operating.
Defective regulator.
Defective alternator.
TOOLS AND EQUIPMENT:
1 - Voltmeter (Digital type preferred.)
1 - Ammeter (Digital, Inductive type preferred.)
1 - 12 gauge lead, 12 inches long, with alligator clip
at each end.
BATTERY CONDITIONS AND CHARGE
VOLTAGE REACTIONS:
NOTE: Until electrical system component tempera-
tures stabilize, these conditions may be observed dur-
ing cold start voltage tests.
Maintenance type:
Immediately after engine start, system volts are
lower than regulator setpoint with medium amps.
3-5 minutes into charge cycle, higher system volts
and reduced amps.
5-10 minutes into charge cycle, system volts are
at, or nearly at, regulator set point, and amps are
reduced to a minimum.
Low Maintenance types:
Same as above, except cycle times may be
longer.
M13-7
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Troubleshooting
