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Electrical troubleshooting

Apr 14, 2008
Make no mistake about it, there’s no way you can become an expert mechanic or electrician overnight. Top-flight, crackerjack marine technicians are few and far between and the really good ones usually have two things going for them. One, they are usually natural born gear heads. Two, they have experience. These men and women have been troubleshooting and repairing things for a long time, and not just marine mechanical and electrical systems.

Where does this leave the electrically inexperienced but ambitious voyager who isn’t a gear head? Fortunately, it’s not as bad as it sounds. It is possible to improve your electrical troubleshooting and technical communication skills (you frequently must be able to accurately explain your problem or symptoms to others in order to get help). If you can carry out basic diagnostic troubleshooting and repairs using commonly available tools and communicate efficiently with someone more knowledgeable than yourself, your chances of resolving your problems or electrical failures improve considerably. In what follows, I’ll attempt to impart the necessary information and wisdom so that you’ll have a fighting chance when an electrical failure rears its ugly head.

Tools of the trade
Before you begin your career as an electrical troubleshooter, you’ll have to invest in a few essential tools. Begin with a good set of wire cutters, strippers and crimpers. A variety of both manual and automatic strippers are available. My preference is for the former; however, if you don’t do a lot of wire stripping, you may opt for the convenience and foolproof nature of the automatic variety. Where strippers are concerned, choose a set that does its stripping forward or ahead of the pivot point. This makes it easier to reach into a space with limited access in order to do your stripping. Avoid tools that claim to be an all-in-one stripper, cutter and crimper, I’ve never found one that did all of these tasks well. Get a dedicated version of each that feels right in your hands and works well. Use each one of these tools before you need to.
Handy test light

Another valuable but often-overlooked electrical troubleshooter’s tool is the once ubiquitous 12-volt test light (or 24 volt if that’s how your boat is wired). When I first began working in this industry, this was the marine electrician’s primary troubleshooting companion. It’s nothing more than a 12-volt light bulb housed within the handle of what looks like a transparent screwdriver. A pointed metal tip allows the user to probe electrical connections while a ground is achieved through a short cord, at the end of which is an alligator clip. For ordinary electrical troubleshooting, (as opposed to electronic troubleshooting or instances where exact voltages must be ascertained) as well as for tracking down poor or broken connections, this tool is ideal.

Place the alligator clip on a good ground such as the battery negative post, a negative buss bar or equipment chassis/engine block, and then use the tip to probe connections and you are in business. Verify the ground connection before you begin troubleshooting by placing the probe tip on a known live DC positive source and beware of using painted surfaces like engine blocks for grounding, as the paint often acts as an unwanted insulator. Because these tools were originally designed for automotive applications, the lead, the wire between the screwdriver-like illuminating handle and the alligator ground clip, is often too short (it’s designed to work on an automobile, where there’s always a good ground, the chassis or frame, nearby).

If you decide to add one of these handy devices to your voyaging toolbox, consider lengthening the lead to 20 or 30 feet (longer or shorter, depending on the length of your vessel). This will allow you to connect the alligator clip to a known good ground such as the battery negative terminal, while you do your probing elsewhere, under the instrument panel, at the windlass, in the bilge, etc. Keep in mind, the test light can be used to find a good, or troubleshoot a poor, ground rather than a positive by simply connecting the alligator clip to a positive source such as the battery post and then probing suspect grounds with the tool’s pointy end. Be careful, however, not to use this tool for troubleshooting delicate electronic equipment, the load of even the small flashlight bulb within the tool may damage sensitive circuitry. This tool is primitive, it works well for common electrical (not electronic) troubleshooting of lighting, motor and pump circuits.
 
Serious troubleshooting tool
For more serious troubleshooting and repair operations, more serious tools may be required. The most useful and important of which is undoubtedly the digital multimeter (DMM), also known as a volt/ohm meter (VOM). This tool has revolutionized and simplified marine electrical and electronic troubleshooting and repair work. While its needle-equipped analogue predecessor is also useful, it will perform many of the same troubleshooting and measurement functions as the DMM, today’s digital versions are accurate, versatile, affordable and somewhat easier to use than the older multiscale analogue models, particularly for the less experienced user.

Scores of different makes and models of DMMs are available, many of which can be had for under a $100. Nearly all of these will carry out the most common and useful measurements, AC and DC volts and amps, as well as resistance and continuity. With these functions, you will be able to troubleshoot 95 percent of all onboard electrical faults. More advanced DMMs (and advanced doesn’t necessarily mean exorbitantly expensive) will also allow you to measure, among other things, frequency, which can be useful when troubleshooting or repairing a generator, inverter or if you suspect something out of the ordinary with dockside supplied power (the latter may be the case in less developed regions of the world).

Although a number of high quality, affordable DMMs are available, my preference has been for those manufactured by the Fluke Corporation of Everette, Wash. The multimeters manufactured by Fluke are renowned for their accuracy, durability and reliability. The unit I currently own, an ET-88 (the current version is called an 88V) has seen hard marine service for well over a decade. I’ve dropped it countless times, stepped on it, sat on it and gotten it wet and it has yet to suffer a malfunction. For more information visit Fluke’s Web site at www.fluke.com. Other DMMs are available; many voyagers I know carry the affordable Craftsman Professional True RMS AC/DC Clamp Ammeter, model 73755, which has the added benefit of including an inductive ampere clamp as well as an infrared pyrometer.

It would be difficult to overstate the value of not only owning a DMM, but learning how to use one as well. Here’s an example of just how useful and important this tool can be. A year or so ago I was in regular email correspondence with a full time live-aboard cruiser who was sailing amongst a group of islands off the east coast of Belize (these islands contain two of only four atolls in the western hemisphere, one of which, Lighthouse Reef, was this vessel’s destination). Several months prior, the boatyard I managed at the time replaced this vessel’s 5-kw AC generator with a 175-amp, 12-volt DC model.

His first email indicated that he could not get the generator to crank or turn over, much less start. Because this savvy voyager owned and knew how to use his DMM, I was able, through half a dozen emails, to guide him through the electrical troubleshooting process of checking voltage and continuity at a number of locations throughout his electrical system. This task was made easier by the fact that I too had a set of schematics for the installation, but even if I didn’t possess these, the troubleshooting process could have proceeded, albeit at a slower pace. We eventually ascertained that a wiring connection supplying the key switch, and thus the cranking circuit, had failed, probably as the result of corrosion caused by a defective, leaking exhaust elbow. A temporary jumper wire attached to this terminal had the generator humming away in no time. He worked on tracking down the problem and applying a permanent fix after completing his ten-day passage. A happy ending to a potentially vexing problem to be sure, particularly since this vessel relies on DC power for all of its refrigeration needs.

On average, I receive a call or email a week from vessels as near as my own backyard, the Chesapeake Bay, and as far as the Indian Ocean seeking troubleshooting assistance that is more often than not electrical in nature. Invariably, my first question is, “do you have aboard and know how to use a multimeter?” If the answer is yes, as was the case for the DC generator scenario, chances are excellent that I or someone who is a skilled troubleshooter can talk the user through a process that will result in a resolution to, or at least the discovery of, the problem (or, preferably, with a little bit of experience, the user can carry out the troubleshooting sequence on his or her own). If the answer is no, on the other hand, then there is often very little that can be done other than to say, “Wiggle all the connections and check for loose wires.” Regrettably, the latter stories far outnumber the former.
Measure high current
A useful accessory or addition to the DMM is an inductive amp clamp. In some cases this may be integrated into the meter (as in the case of the aforementioned Craftsman model) while others are stand-alone units. Because even the best DMMs will only measure about 10 amps of load through the meter’s own circuitry, any device drawing more amperage than this cannot be measured with the standard meter. With the addition of an amp clamp, however, loads measured in the hundreds of amps may be accurately and safely measured. Using inductance or magnetism generated by electric current, amp clamps are able to make these measurements without physically touching the cable or wire whose current is being measured (this is the same way most electrical panel meters measure amperage). This makes them particularly convenient and easy to use.

Amp clamps are ideal for measuring everything from the current your engine’s or generator’s starter draws (it’s a good idea to measure and record this when everything is working properly so you’ll have a reference for future troubleshooting) while it’s cranking to the loads imposed by inverters and bow thrusters and most are capable of measuring AC or DC amperage. The amp clamp I use, which is also a Fluke, an 80i-410, measures both AC and DC current to 400 amps. The newest version, the i1010 can measure 1000 amps DC and 600 amps AC. One especially useful safety-related task an amp clamp can perform is checking shore power installations for fault or leakage current that is traveling through the water surrounding the boat. Placing an amp clamp around an entire energized and loaded shore power cable (normally, other than for this test, the clamp is placed around a single rather than multiple conductors), should balance or cancel all readings so the meter shows zero, provided everything is wired and operating correctly.

However, if some of the shore power current is returning to ground via the bonding system and sea water, then an imbalance will occur, which the meter will read (although if fault current is flowing through the shore power cable’s green grounding wire, the meter will not reveal this problem). Especially small current readings, less than an amp or so, may require the use of a dedicated clamp on, leak detector-type meter such as a Fluke 360.

This is an interesting and worthwhile assessment you can perform on your own vessel as well as othera on your dock, and you don’t even have to touch the shore power cable in order to do it.

Make no mistake about it: if the meter shows any current reading, then this is a potentially dangerous situation both aboard the vessel and in the water surrounding it, and it requires the immediate attention of a qualified, preferably ABYC-certified marine electrician. 

Contributing editor Steve D’Antonio offers consulting services to boat buyers and boat owners as well as to boat builders and others in the marine industry through his company Steve D’Antonio Marine Consulting LLC. You can visit his website at www.stevedmarineconsulting.com.