Electronics Troubleshooting

Know how to diagnose issues that can crash a boat's electronics.

Electronic equipment problems always seem to crop up at the worst possible time. The chartplotter bites the dust on the way out for a day of fishing, or the depthsounder blanks out during a transit of some questionable channel. Tech support is a wonderful thing, but self-reliance and the ability to recognize and fix simple problems is even better. A few basic troubleshooting tips can help bring ailing electronics back online.

The first step in troubleshooting any system or piece of electronics gear is something owners should have done before the problem even arose: read the owner’s manual. Having a basic understanding of how the gear or system functions and is installed (e.g., a block diagram) before troubleshooting begins is extremely helpful in recognizing and locating common problems. Most manuals have a basic troubleshooting section, which can get things moving.



The Basics

When a piece of electronics gear fails to turn on, start by checking the power connection at the unit for looseness or corrosion. If the DC power panel has a voltmeter installed, take a quick look to verify it shows the correct voltage and that all required breakers are on. How many of us have realized a “problem” was actually caused by a battery switch or circuit breaker being in the off position?

For electronics that work intermittently or lose certain functions, check the remaining plugs or wire connections, which can also suffer from corrosion or come loose over time due to vibration. As odd as it may sound, some problems can be corrected by simply disconnecting cable plugs and plugging them back in. The same is true for inline cable connections, which can loosen due to excessive movement or vibration if not secured or mounted properly. Trace the cable runs to see if there any problems such as breaks or damage.




If a unit powers up but nothing shows on the display, start simple and check the display brightness and contrast settings. These settings often get adjusted on purpose — to preserve night vision, for example — or by accident to the point where the display is no longer visible under different lighting conditions.

Other control features can generate what I like to call “operator induced anomalies.” If the radar fails to pick up targets, for example, verify it’s on the correct range setting and that the gain/sensitivity features are adjusted correctly.



Voltage Checks

If all the connections are verified to be tight but the problem persists, it’s time to get technical, break out the multimeter and look for hardware problems. Every boat should have a multimeter aboard. Seriously, they can be purchased for as little as $6 at stores such as Harbor Freight. Stay away from light pen–type voltage testers; they can measure if there’s voltage but not how much, which is a critical troubleshooting flaw, because many electronics fail to operate if the voltage drops below a certain point.

To check the power to a piece of gear, turn the unit off and disconnect the power plug or access the terminal strip where power is connected. Then verify that battery switches and breakers are in the on position. Set the multimeter to DC volts and measure the voltage by connecting the meter’s negative probe to the equipment plug negative lead and the positive probe to the positive lead. (A reversal of the probes will cause the meter to display a negative reading.)

A voltage reading of “0” indicates no power is reaching the unit, pointing to an issue such as a tripped breaker, a blown fuse, a loose connection or a broken wire. Note one thing: If a fuse “blows” multiple times when replaced, it should be considered a symptom rather than the problem.

A low voltage reading indicates low battery voltage or possibly additional resistance in the line, such as a corroded or faulty connection. Verify that the correct amount of power is leaving the breaker panel, then work toward the equipment to identify the problem. If the voltage is incorrect, then verify the battery voltage is correct and proceed from there.

Another thing to consider is how steady or consistent the voltage is during equipment operation. Some electronics draw more power during certain operations; a VHF radio when it is transmitting vs. receiving is one example. While it may show a “full” 12 volts at the power plug when the radio is disconnected or simply turned on, that voltage can drop well below a usable level when the radio is keyed to transmit. This is often due to a weak battery or possibly a corroded connection. Monitor the DC panel’s voltmeter (or use a handheld one) while keying the radio to see if the voltage drops.



NMEA 2000

While standalone electronics will have their own dedicated power plug or source, newer electronic systems will likely be powered by an NMEA 2000 (N2K) trunk or backbone. If the system is installed correctly and was working previously — and the voltage supply is correct and all the plugs and connections are good — then the problem could be with the backbone itself. Meters that allow owners to test N2K backbones are pricey, more than $600. If the problem lies with the backbone, it’s likely time to call in a professional.