fuel gauge installation

[mikesh]

i am installing a fuel gauge to be connected to the sender unit in the inboard fuel tank on my sailboat. All the online diagrams suggest drawing the power to the gauge itself by connecting the power lead from the ignition switch output which makes sense. BUT my gauge unit housing the tacho,oil pressure, voltmeter etc is a sealed unit and the big bunch of wires coming from within through the rear of the unit makes no sense to me. So identifying the correct ignition wire seems a nightmare!
Would there be an issue by connecting the fuel gauge, which i think would draw little power? directly to the instrument breaker on the distribution panel breaker?
Any advice would be appreciated.
Thanks,
mike

 

[jssailem]

Mike, the way I read your query, leads me to assume you are not familiar with the way a fuel gauge works. Is this a correct assumption?

 

[SG]

Generally you want to draw the power only when the ignition switch is turned-on. Otherwise you could drain your battery; and, the gauge will be running a lot of hours.

 

[dlochner]

What kind of engine? There must be a way to open the back of the panel. It may require unmounting the panel and then opening it up.

Another alternative is to get power from another circuit that can be turned off. My fuel gauge is wired to the electronics circuit. Or put in a separate circuit with its own breaker.

 

[Ron20324]

Considering how many posts we get about non-working fuel gauges, I'd suggest a switch that you can turn on only when you want to look at the gauge. Kind of like stopping your anemometer's wear from spinning all winter.

 

[Gene S]

I have a dedicated breaker for engine instruments. Mine is wired to that. You could wire it to one similar like electronics.

 

[JimInPB]

The wire that you are looking for should be purple if the boat is correctly wired to ABYC color code standards, https://www.defender.com/pdf/abyc-wire-color-chart.pdf

I've never seen a boat where I couldn't find a hot lead off of an ignition switch, but if that is the case you have, then you can power it from any 12vdc source. As was said, something switched is preferable. Something with a low amperage fuse would be my preference. I don't like the possibility of having a lot of amps inside my fuel tank in the event of an electrical problem.

Also, be aware that there are two types of gauges & two types of sending units. One type is the US standard & the other is the European standard. The number of ohms in the sender is different. The US senders are around 30 ohms full & 240 ohms empty. Euro senders read 10 ohms empty & 180 ohms full. If your gauge works sort of backwards, you probably have mixed the two types.

 

[jssailem]

If your gauge works sort of backwards, you probably have mixed the two types.

Or wired it neg to pos not pos to neg.

 

[mikesh]

Thanks for all the advice. My biggest problem is that the instrument panel is extremely difficult to access from the rear and the front was very well sealed by the previous owner. Thanks especially to Jim in PB - the color chart is very helpful & hopefully there is a purple wire amongst the large bunch otherwise i will most likely run an independent circuit with switch as i only really need the fuel info occasionally. mike

 

[Scott T-Bird]

There really is no reason to draw power from the instrument panel wiring harness. Why take a chance fouling your wiring harness? I put mine on a different circuit and read the gauge at the nav station in the cabin rather than on the instrument panel. Like you say, there isn't a constant need to monitor it in the cockpit.

 

[SG]

I put mine on a different circuit and read the gauge at the nav station in the cabin rather than on the instrument panel. Like you say, there isn't a constant need to monitor it in the cockpit.

While it's not essential in terms of location of the gauges and their wiring. but we like the gauges at the helm:

• If you're low on fuel on that dark and stormy, seeing it in the cockpit is helpful;
• Each time you turn the engine key on, it's part of our "mental" start-up procedure to get a sense for the fuel level.
• I find it helpful is to be able to monitor fuel fills by watching the gauge.