Fuel tank level sender question

[KnotSure]

Okay, I warned you guys I'd have a lot of questions, still trying to figure out where everything is on this boat, and discovering a lot of "improvised" things that have been done to her previously. This, however, I don't think falls in that category. I'm trying to find out where the fuel tank level senders are, my starboard tank isn't reading anything, so I'm trying to first determine if it's the sender or a break in the wire between the sender and the helm. In the engine space, the fuel tanks go all the way up to the top of the space, so there's no access there. When I look above there (under the sofa, etc) I can't find anything either. I've actually got the original owner's manual AND the parts catalog, and looking at the diagrams/schematics, I don't see anything there either. Any ideas?

[km1125]

I didn't have a 455, but my manuals didn't show any access hatches for that kind of stuff, but they were there. I didn't even realize it until quite a long ways after I had the boat.

Are you saying you looked up from the bottom (where the tank is) and you don't see any access hatches?

I would also just wiggle the wires at the sender to see if it might be a corrosion issue. There should be a sensor wire and a ground, so check them both. I had that problem on one of my tanks and I eventually replaced the ring connector which solved the issue. Also, do you have a toggle switch for the gauges, or separate gauges for each tank? If a switch, you might check the connections there too.

[KnotSure]

I'm saying I can't even see/reach the top of the tanks, they go all the way up to/through the top of the engine room. And I can't find anywhere in the salon above that even vaguely resembles an access hatch (under the sofa, in the AC/DC switch panel cabinet, etc). The only place I can find the wires for the senders is at the helm, separate gauges for each tank.

[km1125]

Ah, I see. Hopefully some other 455 owners will weigh in if they've been able to figure that out.

[Viper]

Do you see any wall panels above the tanks in the salon that are removable? Might be behind a sofa or other piece of furniture, the back wall or floor in a cabinet, etc.

[buster53]

On my boat, I have a couple bilge access panels hidden by carpet. I have to pull the carpet up to be able to get to them.

[g36]

Have you verified the guage works? And power to it? If the sending wire is grounded the guage should read full. You will at least rule out the guage.

[Viper]

I agree with g, grounding will give you a full sweep of the gauge and usually peg the needle. If you do it at the gauge, you'll confirm the gauge works. If you do that at the sender and get the same result, you'll confirm the gauge and the wiring from the sender to the gauge is okay including any plugs along the way. Still, you should check and make sure all connections are clean and tight including any plugs. If all is well there, it's likely your sender and that can be confirmed with a test meter. Also check that the grounding connection to the tank is good. The other thing you can try to narrow down the culprit is to swap the wiring at the gauges and see if the fault follows the wiring, use jumpers if you have to.

[KnotSure]

Found the senders by accident while chasing down an HVAC issue! They were up off the floor level behind the backrest cushions of the sofa.