Current Output Test - Mercury MerCruiser MCM 454 Mag MPI Service Manual

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SERVICE MANUAL NUMBER 23

Current Output Test

Perform this test to check if alternator is capable of producing rated current output, using

a 0-100 amp DC ammeter.

Be sure that engine compartment is well-ventilated and that there are no gasoline

vapors present (during the test) to prevent the possibility of an explosion and/or a

fire, should a spark occur.

1. Disconnect negative (–) battery cable from battery.

2. Disconnect ORANGE lead from alternator output terminal and connect ammeter in

3. Reconnect negative battery cable.

4. Remove coil wire from distributor cap tower and ground it to block. Turn on all accesso-

5. Turn off accessories and reinstall coil wire. Start engine and adjust engine speed to

6. If reading is low, stop engine and connect a jumper wire between alternator output

7. If reading is now within specifications, diodes are faulty. Disassemble alternator and

8. If reading is still low with jumper wire connected, perform "Voltage Output Test," follow-

90-861326--1 MARCH 1999

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series between lead and output terminal. Connect positive (+) side of ammeter toward

output terminal.

ries and crank engine over with starter motor for 15-20 seconds.

1500-2000 rpm. Quickly observe ammeter. Reading should be at least 30 amps.

terminal and regulator terminal. Repeat Steps 4 and 5.

replace rectifier as explained under "Alternator Repair," following, to determine if fault

is in regulator or alternator.

ing, to determine if fault is in regulator or alternator.

Output Wire - ORANGE

Ammeter (0-50 Amps)

Regulator Lead

Output Lead (Orange)

CHARGING SYSTEM

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