D2-6 24 VDC Electric Supply System D02023
ON VEHICLE TROUBLESHOOTING GUIDE - SELF ENERGIZED
ALTERNATOR
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 regula-
tor 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.
NO VOLTAGE OUTPUT
Causes of no voltage output:
• No drive belt.
• No battery (B+) voltage at alternator's “B+”
terminal (except isolator type systems).
• No “link” from “R” terminal to energize (“E”)
terminal 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
temperatures stabilize, these conditions may be
observed during 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.
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