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If more than one wire is connected to the alternator output
terminal, clamp around ALL these wires.
Test
In the following test, alternator should be turning at
approximate rated speed. Most heavy duty alternators are rated
at 5000 rpm. Check manufacturer's specifications for specific
alternator being tested.
1. If off, start engine and make sure all vehicle electrical loads are
turned off. Speed up engine. Turn on and adjust carbon pile until
ammeter reads its highest value. Record this reading.
2. Turn off carbon pile and engine.
3. If reading is zero (no output), magnetize the rotor with the
alternator hooked up normally. Momentarily connect a jumper
lead from the battery positive (+) to the alternator relay (R) or
indicator (I) terminal. This procedure applies to both negative
and positive ground systems and will restore the normal residual
magnetism.
4. Repeat steps 1 and 2. If output is still zero, replace the
alternator.
3-32. ALTERNATOR REPLACEMENT.
of the following conditions exist:
1. Alternator output voltage exceeds 15.5 volts (paragraph 3-30).
If alternator has separate regulator, use the appropriate regulator
service bulletin to isolate the defect.
2. Alternator output current is not within 10% of alternator rated
output (stamped on alternator case). Examples: 30-SI - 105 amps,
26-SI - 85 amps, and 21-SI - 100 amps.
3-33. COMPLETION OF ALL TESTS
Make sure that all test instruments have been removed from the
vehicle and that the vehicle wiring, if altered, has been returned to
the operational state.
NOTE
NOTE
Replace alternator if either
FIGURE 3-10. Amperage Output Test
CARBON PILE
DP-1028
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