Ignition On - Engine Running At Fast Idle; Ignition On - Engine Running At Idle; Motorcraft; Base Voltage Test/No Load Test - Ford LSG 875 Service Manual

4-07
CHARGING
4-07
TESTING (Continued)
Test 4 - Ignition On - Engine Running at
Fast Idle
Voltage indicated is usually 13.9 to 14.7 volts
depending on regulator ambient temperature.
High voltage may be due to a poor ground connec-
tion. If ground connection is not faulty, regulator
will require replacement.
IGN 4
YELLOW
\ 4
13.9 14.7
1, /,
- m
t
DC VOLTS
Test 5 - Field Term Disconnected
Voltage Regulator Plug Disconnected
Battery Terminal
Shorted to Field Terminal
ignition On -
Engine
Running at Idle
This test isolates defect to either the alternator
or regulator. If voltage at auxiliary terminal rises to
15-16 volts now, when it did not in Test 4 with
regulator connected, then defect is in regulator
and it should be replaced. If voltage does not rise
at auxiliary terminal, defect is in alternator stator or
rectifier diodes, if field circuit checked out prop-
erly. For defects in stator or diodes, remove
alternator.
NOTE:
On integral regulator
units, remove reg-
ulator completely. .
GREEN FLD WIRE
DISCONNECTED
DC VOLTS
MOTORCRAFT
When performing charging system tests with a
voltmeter, turn off all lights and electrical
components.
CAUTION: Be
sure field terminal connector is
installed
on
the "Field" terminal stud at alter-
nator and not the ground stud.
Always disconnect the connector plug from
the regulator before checking alternator out-
put with test probes or a jumper wire.
Always disconnect the connector plug from
the regulator before removing the regulator
mounting screws. Removing the connector
from an un-grounded regulator with the igni-
tion switch on will destroy the regulator.
Never attempt to polarize or test the alternator
by grounding the field circuit, as this will de-
stroy the regulator.
Base Voltage Test
1. With ignition off and no electrical load on,
connect the negative lead of the voltmeter to
the negative battery cable clamp.
2. Connect the positive lead of the voltmeter to
the positive battery cable clamp.
3. Record the battery voltage reading shown on
the voltmeter scale (base voltage).
No Load Test
1. Connect a tachometer to the engine.
2. Start the engine and increase speed to ap-
proximately 1500 RPM. With no other elec-
trical load, the voltmeter pointer should move
upward (increase), but not more than 2 volts
above the base voltage (first recorded battery
voltage reading above). The reading should
be taken when the voltmeter pointer stops
rising. It may take a few minutes to reach this
point. If the voltage increases to proper level,
perform Load Test. If the pointer continues to
rise, perform the Over Voltage Tests. If the
voltage does not rise to proper level, perform
the Under Voltage Tests.