Mercury MerCruiser D2.8L D-Tronic Service Manual page 383

SERVICE MANUAL NUMBER 22
Perform this test to determine if voltage regulator is operating correctly, using a 0-20 volt DC
voltmeter.
IMPORTANT: Battery MUST BE fully charged (1.260 or above specific gravity) to ob-
tain proper voltage reading in this test. If necessary, charge battery with a battery
charger or allow engine to operate a sufficient length of time to fully charge battery
before taking reading.
1. Connect positive (+) voltmeter lead to positive battery terminal and negative (–)
voltmeter lead to negative terminal.
2. Start engine and operate at fast idle until engine reaches normal operating temperature.
Adjust engine speed to 1500-2000 rpm and observe voltmeter for highest reading.
Reading should be between 13.9 and 14.7 volts.
3. If reading is high, check for a loose or dirty regulator ground lead connection. If
connection is good (and sensing circuit checked out good in Circuitry Test), voltage
regulator is faulty and the alternator must be replaced. Ensure that battery cables are
disconnected before attempting to remove alternator.
90-860074--1 FEBRUARY 2002
a - Excitation Wire - PURPLE
b - Sensing Wire - RED or GREEN
c - Ground Wire - BLACK
d - Output Wire - BLUE
e - Voltmeter (0-20 Volts)
d
c
b
a
CHARGING SYSTEM
e
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