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

AC Power Sources

AC power sources consist of shore-power iso-

lation transformers and AC generators, both

of which are AC current producers. The trans-

former is a point of distribution on board the

boat; it is supplied by the shore-power feed

but electrically isolated from it. Because the

tools of choice here are the full arsenal of AC

diagnostic tools already mentioned, no flow-

chart is presented.

• Check amperage and voltage outputs: use
  the SureTest tool (Chapter 4).

8 marine troubleshooting

Use the SureTest tool (Chapter 4) to

completely diagnose all power and grounding

faults. This tool will save you many steps

over using conventional diagnostic methods,

and it will perform tests that no other tool

can perform.

Use a multimeter to confirm presence of AC voltage. Then isolate each cable and test for

resistance with an ohmmeter. There is no safe way to check cabling under load, and no

way to test trip rates and times.

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Poor performance

(power supply

suspect).

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AC Resistive Loads (1)

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AC Resistive Loads (2)

Perform safety check for ground fault

leakage.

Use a high-resolution clamp-on AC leak

tester to isolate the source of AC

leakage current by process of

elimination (Chapter 10).

Use a “split cord” to open the grounding conductor, and check current flow with

a high-resolution ammeter in series with the ground wire. Takes more steps and

has more potential dangers than a high-resolution leak tester.

Suspected

AC leakage.

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AC Resistive Loads (3)

Conduct power consumption analysis.

Use the WattsUp? tool to analyze the

equipment’s power usage over time (Chapter 6).

Use the WattsUp? tool to calculate operating

costs of your equipment.

No prior methods existed for performing this task.

Excessively

high electric

bill.

Engine Instrumentation (2)

In the case of a tachometer, the calibration or cylinder number selector on the gauge may be set

incorrectly. The number the gauge is set to should be the same as the number of cylinders in the

engine.

In the case of oil pressure, fuel, and other level gauges and temperature senders, the sending unit

could be faulty. Try a new sender or check resistance values against a known specification provided by

the instrument manufacturer as in the previous flowchart (if you are able to find that information).

The methods described here follow traditional procedures. Sometimes the good old DVOM is still the best way!

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Instrument

reads

inaccurately.

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