Need help with Fuel gauge/Sending unit

[Basszilla4]

I recently installed a set of Faria gauges. Speeometer (0 - 65mph), Tachometer (0 - 8k rpm), and Fuel (E - F). Everything works great except fuel gauge. These all were bought off eBay in a set and were used. Boat never had a fuel gauge so I bought a Moeller 3 wire sending unit and installed into tank. No float arm. At first, couldn't get fuel gauge to work/function. I checked the ohm's from sending wire on sending unit. Seemed to work fine. Don't remember exact readings, but if I unscrewed sending unit and slid up and down in fuel tank, the ohms readings would change.

So, I thought it was a faulty fuel gauge. I sent gauge back to Faria and they sent me a brand new fuel gauge. Still wont work. Boats motor is a 1973 Johnson 65hp. Here is how everything is hooked up:

All three gauges have their 12v lights hooked in a sequence through a fused toggle switch. All work fine.

Tachometers 12v power comes from ignition key purple wire from control box. Ground is off instruments lights ground, and signal wire is from gray wire from inside control box. Tach works great.

Fuel gauge gets 12v from same purple wire as tachometer in control box. Ground from same instruments lights ground. And signal from fuel sending units signal output terminal.

Fuel sending unit has three wires. Red to battery positive post, black to battery negative post, and white to fuel gauges sending terminal. This unit was bought brand new.

Now, I know its not the gauge being brand new from Faria, and sending unit seems to work. My thinking is it could be how I have it wired. The only thing I notice (and happened with old fuel gauge) is with the tachometer. Before fuel gauge was connected, with key off, the tach needle would read slightly below zero. When key was turned on, the tach would zero out. As soon as I connect sending wire to back of fuel gauge, it causes tachometers needle to fall WAY below zero. Almost to the eight. Tachometer will still zero out when key is turned on, turn key off, and tach needle falls like a stone.

Anybody have any ideas? Anything? Please help. ANY information would be GREATLY appreciated.

Thank you.
Sincerely,
Errol (Basszilla4)

 

[Basszilla4]

Re: Need help with Fuel gauge/Sending unit

I should mention, I tried connecting fuel sending units black wire to ground instead of negative battery terminal with same results. Nothing. Again, please help with any ideas you may have. Getting frustrated here. Thanks again.

Sincerely,
Errol (Basszilla4)

 

[dingbat]

Re: Need help with Fuel gauge/Sending unit

Moeller makes reference to Wema more than once on their website and that unit looks strangely enough like the Wema SS units that came on my boat.

On the Wema units the red is ground and the black wire goes to the guage. Give that a try and see what happens

 

[Basszilla4]

Re: Need help with Fuel gauge/Sending unit

Moeller makes reference to Wema more than once on their website and that unit looks strangely enough like the Wema SS units that came on my boat.

On the Wema units the red is ground and the black wire goes to the guage. Give that a try and see what happens

There is a white sticker on the top of sending unit which indicates what color wires are what. Don't think they would mess something like that up, but will give it a try. Hope I fry anything.

Will post results. Thanks for the suggestion dingbat.

 

[Basszilla4]

Re: Need help with Fuel gauge/Sending unit

There is a white sticker on the top of sending unit which indicates what color wires are what. Don't think they would mess something like that up, but will give it a try. Hope I fry anything.

Will post results. Thanks for the suggestion dingbat.

Hope I DON'T fry anything...lol

 

[TommyA]

Re: Need help with Fuel gauge/Sending unit

What does the third wire on the sending unit do? You said it does not have a swing arm so that makes it a reed type listed on their website. Is that correct?

 

[dingbat]

Re: Need help with Fuel gauge/Sending unit

Here are the Wema installation instructions
http://www.wemausa.com/specifications/FORM-E.pdf

 

[Basszilla4]

Re: Need help with Fuel gauge/Sending unit

What does the third wire on the sending unit do? You said it does not have a swing arm so that makes it a reed type listed on their website. Is that correct?

Don't know on the reed type.

On the sticker on top of sending unit, it reads, Red - Positive, White - Signal, Black - Negative.

Sending unit is a Moeller #395105
Centriod Products Inc.

http://www.centroidproducts.com/3wire.htm

I have everything installed exactly like this (above link) except red positive from fuel sending unit goes straight to battery positive post.

 

[TommyA]

Re: Need help with Fuel gauge/Sending unit

The Positive (red wire) needs to connect to the same terminal in the fuse box as the purple wire. DC current travels from - to +. Because you are hooking straight to the positive side on the battery you are bypassing the gauge. The gauge would work if you would hook the red side straight to the gauge but then it would always be on. Hooking on to the Purple wire will cut the gauge off when the key or master switch is shut off.

Make sure that the connections on the back of the gauge set just like the drawing.

Always be sure with DC current that you don't reverse the + and - wires for components that are made specifically for DC or you could damage them.

And also make sure to let us know when it works!

 

[Basszilla4]

Re: Need help with Fuel gauge/Sending unit

The Positive (red wire) needs to connect to the same terminal in the fuse box as the purple wire. DC current travels from - to +. Because you are hooking straight to the positive side on the battery you are bypassing the gauge. The gauge would work if you would hook the red side straight to the gauge but then it would always be on. Hooking on to the Purple wire will cut the gauge off when the key or master switch is shut off.

Make sure that the connections on the back of the gauge set just like the drawing.

Always be sure with DC current that you don't reverse the + and - wires for components that are made specifically for DC or you could damage them.

And also make sure to let us know when it works!

Hey thanks for that info. I wish I would of came inside a few hours ago to read that post. I went out and isolated completely all wiring to gauge with same results. However, I still had sending units red wire connected to battery's + terminal. Also wasn't working was my livewells. You could hear the pump running but would not circulate any water. That was easy though. The guy I bought boat off of had the wires reversed and when turned on, pump would push water instead of pulling it up to livewells.

I will go out first thing tomorrow morning and try connecting red sending wire straight to back of gauge or purple ignition wire. Will post results regardless of outcome.

Thanks again everybody. Feel I am getting close