Advanced Marine Electrics and Electronics Troubleshooting A Manual for Boatowners and Marine Technicians

testing batteries, charging systems, and starter circuits 29

system test by pressing the “Next” key after

the starter circuit test is completed.)

AC rippleis the amount of AC leakage past

the diodes in the alternator’s rectifier assembly,

which indicates either alternator stator damage

or, more likely, rectifier diode failure or very low

quality diodes. I generally use 0.4 VAC as the

maximum acceptable reading. More than that

will almost surely induce excessive RFI (radio

frequency interference), with the potential for

interfering with electronic systems on board.

(Many of the worst cases of excessive AC ripple

I’ve tested in the field were on newly rebuilt

alternators, which says something about the

quality of the diodes some remanufacturers use.)

For the next phase of the test, turn on electri-

cal loads. The meter suggests automotive acces-

sories such as headlights and the heater blower

fan, but you should switch on the critical loads

as defined in ABYC Standard E-11 for DC

load calculations (see column A in the ABYC

worksheet on page 30). Some typical DC

amperage draw values for common onboard

loads are shown in Table 2-3.

The sequence begins with the unit prompting you to turn
off all loads and idle the engine. If the unit senses a no-
charge condition at idle (common to many diesels with
self-exciting alternators), it may ask you to confirm whether
a diesel is the subject of the test. (Some diesel engines
require the engine to be revved at above idle speed to
excite the alternator into producing a charge.)

Next the unit prompts you to rev the engine for 5 seconds
to a certain rpm level (indicated by a hash mark) with no
electrical loads. The EXP-1000 will tell you when engine
rpm is detected; at that point, hit the advance key on the
meter to move to the data page, which will give the results
of the test with loads off. Then it tests for problems, such as
excessive AC ripple, voltage output, and charging amper-
age values if the amp clamp is used.

Equipment Load (amps)

Anchor light 1—3

Bilge blower 1—8

Bilge pump 2—8

DC refrigeration 5—20

Depth sounder 0.1—4

Knotmeter 0.1—1

GPS/chartplotter 0.1—5

Masthead light 1—2

Radar 4—8

Running lights 3—6

SSB radio 1—30 (30 in transmit mode)

VHF radio 0.7—1.5

Windshield wiper motors 1.5—5 (each)

DC Current Draw

TABLE

2-3

1

2