Here are some basic things to look for and test when you're having issues. Knowing the basics can save a trip or vacation, and being self sufficient lets you better enjoy your time on the water!
Wire Corrosion
Often, high quality wire connectors are overlooked, which can lead to extremely
frustrating issues that can be difficult to track down. Open terminals allow corrosion between the connector and wire jacket, eating away at the strands and causing problems while potentially looking ok at a glance.
We use and recommend marine grade heat shrink terminals for almost everything. Some people only use them in places with the risk of getting wet, but the reality is that a boat is a moist environment, and there are no parts of a boat that aren't affected by the humidity in the air.
Intermittent lights and other devices
Flickering lights, devices that work...sometimes...you know what it's like. This can be caused by a number of things like wire chafe, bad wire connections or corrosion, corroded terminals on the fuse/fuse holder/breaker/switch, and even the internal circuitry of the device itself. Start at the source of power, and work downstream towards the device, inspecting each connection and testing voltage and current at every connector.
Tripping breaker
Immediately when switched on - probably a short somewhere along the wire. Inspect the wire carefully at both ends first. Then with the device disconnected, use a multi-meter and
check for continuity between positive and negative. Inspect the length of the wire, look for chafe or anything that could be bridging positive and negative. Disconnect wire from load side of the breaker, and flip the switch. It could be a bad breaker. If the breaker trips when disconnected, replace the breaker. If the wire, breaker, and connections pass testing, chances are the problem is the device itself.
Often, we see new installations that weren't carefully planned and end up damaging existing wiring. Always check behind that bulkhead when you are mounting the new device or drilling holes.
Batteries draining when away from the boat
There's a good chance that if your batteries are draining in a week or two while away from the boat - and you've turned the main battery switches off - that there are some devices connected directly to the battery. Check the positive terminals on each battery, and the battery side of the main switch.
The only thing that should be connected are safety items. A couple of examples are bilge pumps, smoke detectors, and carbon monoxide detectors.
If you don't have anything more than important safety devices attached to the battery, it could mean that your batteries are getting tired and are in need of care or replacement. Check the water level if it's a flooded battery, or let us come out and test the batteries with our specialized equipment.
Wire nuts
Wire nuts are perfectly fine to use on land, but they are one of the cardinal sins in marine electrical work.
There are two major reasons that you should never, ever, use wire nuts.
They are designed for solid wire. Home wiring normally uses solid wire - meaning it's just one thick strand. When you twist two solid wires together with a pair of pliers, that's a fairly solid connection in itself. Then you screw on a wire nut, and it cuts tiny threads in the twisted wire, ensuring it all stays together. The main problem with this is that you almost always want to use stranded wire on a boat. Stranded wire can't be manipulated in the same way as solid wire, and requires different connectors. Stranded wire is flexible. It needs to be since a boat is always moving. Wire needs to be able to flex with the boat, otherwise it would just break. When you screw a wire nut to stranded cable, it is usually a poor connection and the chances are very good that it will eventually come apart.
There is no water resistance. Going back to the first item on the list - high quality marine heat shrink connectors - stop moisture from entering the connection altogether. Wire nuts do no such thing, and in a home do not need to.
Overloaded terminals
This is an issue we see on the majority of vessels we work on. Instead of using a bus bar connected to the battery, people just connect wire after wire directly to the battery posts. Maybe there IS a
bus bar, but there are just so many wires that the bus bar ends up overloaded as well!
According to ABYC (American Boat & Yacht Council), no more than 4 connections are allowed per terminal.
Check your batteries, bus bars, circuit breakers, and any other terminals for this. While you're at it, make sure that the biggest connectors are on the bottom, and the smallest on the top. Large connectors = high amperage. Small connectors cannot handle that kind of amperage, and can melt/catch fire!