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Troubleshooting marine electronics

Following up on last-week’s discussion about training for boaters who want to expand their marine electronics knowledge, here’s a primer on troubleshooting. Dealer and NMEA course instructor John Barry wrote this for readers of Marine Electronics Journal, which includes installers and others in the trade. In the article, though, John describes an overall approach to the “art” of troubleshooting rather than technical details about specific failures. The steps he recommends should help you work through even complicated onboard problems. At the very least, his advice will help you better understand what the failure may involve in order to discuss a solution with a technical expert.



By John Barry


Troubleshooting is not something that can be taught, it must be learned. Finding the cause of a failure gives the technician a feeling of victory. Understanding how a device should work is essential to determining why it does not. Getting to the cause is a practice in patience, channeling Albert Einstein and Sherlock Holmes equally. This pesky subject is a tough one for an article, but here goes.

When I was in eighth grade I was taught the scientific method. The idea is to create a control group to compare against a variable group. Importantly, this method requires varying one thing at a time in the variable group; the control group remains unchanged. For example, if you plant 10 seeds you may put fertilizer on five but not on the other five. Later, you see the effects of the fertilizer or lack thereof by comparing the control group to the variable group. This is the scientific method in a nutshell. When troubleshooting, our control group, in effect, is the symptom and the ability to duplicate the symptom. We try one thing at a time then check to see if the symptom is solved.


Gather information

When you talk to the operator and get a description of the symptom, this is the ideal time to collect some data. Ask about the failure, when it occurred and what else was happening. The more information you can gather, the better. Ask about prior failures, conditions at time of failure, status of other systems aboard, or anything that can relate to the failure. By asking the right questions, possible causes may be eliminated or suspected. Always ask if it ever worked, the answer may surprise you.


Duplicate the symptom

Once you arrive at the boat, the first order of business is to duplicate the problem. This is a time to be observant. Notice the details, confirm the parameters. Is the boat plugged in and charging? Are the battery switches on? Did the bilge pump cycle when you stepped aboard? Turn on the affected device, listen, look and pay attention. What has been reported and what you observe may not match. Look for common failures; are other devices affected?

Experience tells us what to check on a particular device. There may be a system checklist. If so, this is an excellent way to confirm operation. When checking a device pay close attention to how it behaves. Note spurious behavior such as screen flashing, extra beeps, etc. Turn-on behavior should be consistent. Sometimes there are other devices that are affected by a common cause. If you see something is wrong, try to duplicate the observation. The idea is to duplicate the symptom consistently and repeatedly.

Complex systems can be daunting to understand. Think about what does work. An example could be to isolate a wind instrument from the network backbone, etc., and hook it up as a standalone device to confirm whether it’s ok or not. Dividing a complex network back to understandable pieces allows accurate observations to be made.


Develop a solution

Once we duplicate the symptom, we need a solution. Sometimes there are multiple possible causes. For example if we find a device lacks power to it, we may think blown fuse, broken wire or dead battery, so each must be tested. Performance symptoms like poor range on VHF require measurements to be made to duplicate the symptoms. Measurements of the symptom can range from a simple battery voltage test to a current, temperature or radio test. Depending on equipment type, various test equipment may be required.



When making a measurement, you have to trust your test equipment. I always check my meter at a known circuit. So before I measure for voltage, I take a quick reading from a good power source to test the meter and probes. Get in the habit of using the correct tool for the job and being scientific in your actions. No true contradiction in terms exists in nature, only incorrect terms. When something doesn’t make sense, measure it again. Some devices have self-diagnostics and error logs that may help find failures.


Deduce possible causes

Troubleshooting is a process of deduction. Things fail for a reason and finding that reason is the goal. Fixing what is broken is important, but finding the cause is better. Things can fail due to voltage, corrosion, overheating, and shock among others. The more relevant information you can gather the better.

Experience helps tell us the most common failures and there are certain vulnerabilities that can help figure it out. For instance, we know that saltwater is corrosive, so parts that are exposed to saltwater are likely to fail. Things that perform physical work, like motors and solenoids, may wear out with age. So if the batteries are empty, connections are green, vents are clogged or stuff is cracked, these are not good signs and may be clues. Failure of electrical contacts in relays and switches due to age and exposure happens a lot. Overheated parts may have heat sinks attached, cracked parts may show up with vibration or shock. Calling factory tech support may help.



Substitution. This method uses trial and error to determine if likely fixes are correct. An example is trying a new light bulb to see if the bulb lights or maybe replacing a transducer to see if depth works.

Inspection. Look for telltale signs of the cause of a failure. Don’t discount visual inspection. A close look at things can reveal a lot. A good set of eyes can see loose connections!

Elimination. This determines what does work to find what does not. Test parts of the system individually to simplify analysis and confirm operation.

Deduction. The most powerful tool uses logic to determine causation. When the customer reports that batteries were replaced and now something is dead, you can deduce something was not reconnected during battery replacement.

Curiosity is a common trait for troubleshooters. Knowing some simple tricks goes a long way. Having the correct tools is essential. Troubleshooting an Ethernet network without a network test tool is foolish. Looking for bad power supply is fruitless without a meter or test light. Troubleshooting coax problems without a TDR [this is a time-domain reflectometer, which detects faults in cables and other issues] is difficult. Watch what others do, understand why you do the things you do yourself, and always err on the side of safety. Read technical manuals, ask questions, be observant and always ask how does this work.


Confirm diagnosis

Once we have examined, measured and diagnosed the problem, we must confirm repair. Electronics can be difficult because so many things can conceal the symptom, like software, component characteristics, operating modes, etc., so it is important to follow the scientific method to confirm repeatedly that the symptom, previously confirmed, is indeed solved. Multiple cold restarts are the norm. Turning on peripheral devices and selecting various operating modes is important. Always question yourself, be patient, keep an open mind, reject assumptions, test and verify.


About the author

John Barry is a Certified Marine Electronics Installer (CMET) who owns and operates Technical Marine Support, Inc., a full-service dealership in Pleasant Prairie, WI. He instructs both the Marine Electronics Installer and NMEA 2000 Network courses for the National Marine Electronics Association.


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