Where is my sending unit?

[TonyD]

Hey - I have a 1989 Grady Tournament and recently, it appears that my fuel gauge is reading past empty. The gauges are brand new, just over 2 years old, that were put in with my re-power. The gauge was also working a week ago.

However, I did check the colts to the gauge and I am getting my 12 volts there but now I want to check and test my sending unit. But, my problem is.. not sure where it is.. this pic below is what I believe to be the sending unit but I don't see any wires that I can disconnect and check. It also looks like that if this is the sending unit, I am going to have to pull up the whole floor board to get to it? Anyone know if this makes sense or has a '89 Touney and has run across this before?

 

[Denko]

That is the sending unit, follow the wire in the pic to a connection that goes to the gauge. I don't know anything specific about your model though.

Good luck!

 

[TonyD]

Thank you, Denko for the confirmation. I'd really have to pull up the floor board to see where that wire runs (and even then I might not be able to tell). As it is now, I can't really tell, which is a bummer, because all I want to do is test it - ha!

Does anyone know of another way of testing the unit without pulling off the wire to see if the gauge reacts?

 

[DennisG01]

Did you see if there's any slack in the cable? Is there another access plate nearby? Look feel under the floor for the connector.

You may still be able to remove the sender, if needed. Use a screwdriver bit and a ratcheting box end wrench.

You can test at the back of the gauge, the same way you would test at the sender. The only downside there is that you're not testing the wire between the sender and the gauge to see if it has failed.

 

[Denko]

Did you try following it back by hand? On mine the sending unit wire was only about 1' long...

 

[TonyD]

Thanks guys! So, I was able to find the wires going back to the gauge ...it looks like I have a white wire and a green wire.. the green wire is grounded to the gas tank way underneath. The green and a white travel through a harness all the way up to the helm.

Underneath the helm I can see where the split was made to install the new gauges. The white is spliced off onto another new nice white wire to the gauge and the green ground goes right to the ground on the fuse block. (Not sure I know where the fuse is for the main send wire?) Would there be one? I would assume so. I didn't have the tools on me at the time this evening to try for a proper test since I was just more into just trying to trace the wires but I will give a go tomorrow. I'll follow up later on.

Thanks for your input, much appreciated!!

Tony D.

 

[DennisG01]

Usually a sender wire is pink (standard ABYC specs). But, regardless... a fuel sender wire will not have a fuse. A fuel sender works via resistance.

 

[TonyD]

Usually a sender wire is pink (standard ABYC specs). But, regardless... a fuel sender wire will not have a fuse. A fuel sender works via resistance.

Yeah, of all that I have been reading it should be pink but there is nothing pink coming off of this sender. Actually, there are 3 wires - the white, a black and then the green ties into them and them runs down onto a ground onto the tank. I'l take a picture tomorrow when I have sunlight.

And yup, that makes sense about there not being a fuse! That's why the ohm's fluctuate ( full, empty, half full, etc)

Tony D.

 

[TonyD]

So, I got to the sending unit - of course nothing is easy
Anyway, that wire I thought was white, when I look at it on an overcast day, and wipe the grim away - it really IS pink! So, now I have the sending unit out of the tank but all of my tests are leaving me scratching my head.

First the Ohm meter.. nothing registers, not even when moving the float (which did not appear stuck, seems to move freely). That would tell me, well bad unit. But then I removed the pink sending wire and yet, my gauge remained on empty. Nothing changed there.

So, I went to the helm and removed the sending unit wire from the gauge and still noting happened... Now, I don't know if I have a bad sending unit, a bad gauge - or both - OR just a really bad ground somewhere.

My only other thought was, that maybe the toggle switch at the helm is bad? The lamp on the switch does light up when I turn it on .. IDK, puzzled now... The cause is only 2 years old so I don't see how the cause could go bad that quickly.

Tony D.

 

[Denko]

If you disconnect the sender, it should read ~240 ohms with the float at the bottom (empty) and ~32 ohms at the top (full). Just removing the pink wire creates infinite resistance, which will read empty on the gauge.

 

[DennisG01]

You still need to have power at your gauge (key on) for the gauge to read. When checking the operation of the sender to the gauge, it needs to be grounded (which it was when it was installed). I'm not sure if you are, or are not, doing these things - but that could explain the confusion you're having. If you're just manually checking the sender, itself, then follow the advice above and watch your meter (smooth transition) as you move the float.

 

[TonyD]

Hey, Dennis.. yeah everything was "on".. key turned, battery switch on, etc. Denko, not getting any reading at all, on the meter for ohm's. Part of my issue with this sending unit, there are no posts on the unit, everything is all internal nothing as simple as disconnecting the wire.- so I had to cut the wire, splice it and start from there.

What I think I am going to do now is just get another sending unit, install it and go from there. If it still does not work, maybe I can get Yamaha (or Somers Point Marina) to send me a new gauge since it's only 2 years old...I still have a hard time believing it's the gauge however.

 

[Willy-C]

IIRC disconnecting pink wire will show empty tank (as previously mentioned) and touching the pink wire directly to ground will show a full tank....if that works then your sending unit is n/g.

And it's not a big deal to pull the tank cover, assuming someone didn't use a sealer too strong (like 4200 or 5200). I used regular white RTV silicone on mine

 

[TonyD]

Hey, Willy - I had sealed up the cover about 3 year ago, so I know it will come up rather easily - but, I just did it 3 years ago. haha!

I also just didn't want to do all that if the unit was indeed "good", making extra un-needed work for myself. That all said, I don't know if the unit is good or not, or if it's the gauge since I am getting inconclusive results with my troubleshooting. The only place I am getting anything is at the gauge itself, where I have my 12 volts with a meter. Doesn't tell me too much. But, I did place an order for a new sending unit from Wema. I'll test that before I drop in the tank by hooking it right up to the gauge, see what happens. I might find myself getting a new gauge too, so we'll see.

What I found interesting though, on Wema's website, it says the pink wire is ground and the black wire goes to the gauge. I thought that to be odd since everywhere else I read, the pink is supposed to be the sending wire.

Thanks! I'll update when I get this working

Tony D.

 

[TonyD]

Just updating this . My sending unit arrived. I wired it directly to the gauge and wonderfully, it worked!

I then wired it at the gas tank, with the wires that are running up the boat to the helm to the gauge (where the old unit was connected to) - and that too worked! I am glad that my hunch worked out, not sure why I wasn't able to properly troubleshoot the problem.

Next up, pulling the floor panel up to install the gauge into the tank.

Tony D.