Fuel gauge mod..gone backwards!

I decided as long as I still had a sending unit in my gas tank, I may as well find a gauge so I can actually see the gas disapear. So I find, by doing some research, that the Yamaha sending units work at 0 ohms empty to 90 ohms full. So now I look up various gauges that are on the market and what kind of resistance they need to work. It just so happens that the older (90s and earlier) General motors gauges work at 0-90 ohms! Great. So I install one and hook it up and.....it reads backwards (reads full when the tank is empty and empty when the tank is full)
I can live with that I guess. Atleast I know how to read it anyways. LOL
I guess I'll just take it apart tomorrow and reverse the letters so it reads right. Just had to rant.

 

That's not a bad hack.
I once had a Toyota gas gauge that was dead from full down to 1/3 tank; read full at 1/3 tank, and slowly started rising from that point 'til empty. I ended up just selling that sucker....with no gas in it, lol.

 

spin the gauge around 180 degrees and change the letters like you said. That might work as long as the needle doesn't just fall down.

 

Are the polarity backwards on the two gauges? One positive ground and one negative? Would make it read backwards I would think.

 

Reversing the polarity didn't work. I swapped the wires around and no go. I even tried changing them on the sender plug, but that won't do it either.
I think reversing the face will be my only option with this gauge.
I have a stock gauge, which works, but I need to fabricate some kind of housing for it. I got it out of another pair of gauges (just the insides of the gauge) thanks to one of the forum members.
I already went thru trying to modify an old sending unit to make it work backwards, but that didn't go so well. The variable resistor on the sending unit is made in such a way that it is just about impossible to re-wire to work backwards (by me anyways)
So although I'm a little frustrated, I'm not done with this thing just yet.

 

Update:
I just got back from the shop. I got'r workin' jes fine. I removed the glass gasket, and the needle to get the face off. Took'r in and using a fine, fine brush and some lettering enamel, I changed the "F" to an E and the "E" to an F. There now I feel better!

 

Do you have a part number for the gas gauge?

 

The gauge is an Equus brand gauge for GM applications (don't have the actual part number right off hand) Any of the GM gauges work the same from Equus. The Yamaha sending unit works by sending 90 ohms tothe gauge when empty and 0 ohms when the tank is full, and the GM gauges are the complete opposite.
By reversing the letters E and F, it works alright for now. I'll find something that works like it should eventually.

 

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Just out of curiosity, can I purchase a sending unit and install a gauge on my 650 tank?

 

That would require major surgery on the tank of your 650. How precise are you at cutting holes in steel? Be sure to completely drain and clean out your tank before doing this ensuring no flammable vapors/liquids are left in the tank, otherwise one spark and ...

 

Fair enough. Don't think I'll do it. Was just curious.

 

You can do what I am doing: put an XJ750 tank on an XJ650. This would give you 5 gal capacity rather than 3 - fewer stops, longer range, ...

 

Yeah, can you post a picture of that when you're done. I'm curious about how it looks.

 

I did find a gauge (VDO) that is rated 90 ohms empty and 0 ohms full, which is just what the doctor ordered. It sells for 25, so I may go that route.
I have re-labeled the present gauge by changing the letters around, so everything works good for now.

 

I searched high and low and cannot find a fuel gauge that registers 90 ohm as empty 0 ohms full...
Millions of the opposite though.
I've only used Google, haven't called anyone yet...

 

my project bike, kawasaki kz (gt)550 shaft '83 reads 0 ohs when full, info might be of some little use to someone.

 

SirHedgeDog,
Lookie here!

http://www.bobsgauges.com/servlet/the-6 ... vel/Detail

 

PainterD,

I was wondering about that when you mentioned it before. It says it is for a tube type sender. Is that what we have in the XJ750 Maxim tanks? I know it uses a float on an arm to the sender, like the old toilet float things. The ohms are correct, but will it understand the output from the sender? It would be great it if did send totally variable ohms to be read by a gas gauge, but I got the impression from earlier that it just sends 90 ohm or 0 ohm ... thoughts?

 

variable.........

 

Yes the senders in the Maxim/Seca tanks is a float on the end of a long rod that moves a little feeler across a variable resistor to send the signal to the gauge. It sends 90 ohms of resistance to the gauge when the tank is empty and 0 ohms when the tank is full. That's what makes the needle move up and down on the gauge.
*Just another note - if your sender isn't working, you can remove it from the tank and simply fix it. Mine got a little corroded over time (musta been a little rust in the tank) and I used fine sand paper on the variable resistor to make the feeler make better contact with it. It's pretty simple to do actually. There's a small steel cover over the unit that needs to be removed, so just be careful removing and re-installing it (small tabs the bend to remove it) Just make sure the little feeler arm makes contact with the variable resistor wires inside. I cleaned mine and hooked it up to the bike to make sure the needle on the gague moved when I moved the arm up and down. Just a thought.

 

Thanks. I looked at the thing and figured it needed to be cleaned, but all I saw were those tabs and I wasn't sure I wanted to go bending them ... Looks like I need to though ... But the other part of the question ... this is a "tube sender"? Because that is what the gauge said it required. Forgive the stupidity but I have no idea how flexible these things are and know little to nothing about electrical devices ...

 

I'm not familiar with a "tube" sender, so maybe someone else will have an answer for you.

 

The gauge I just bought says 0-100ohms for the fuel gauge....what will that do with the seca750...

Is that extra 10 ohms important? Can I rewire the sending unit (I saw some posts online about that)

Anyhow, I hope someone sees this old post, and can help me out!

 

If you use a 100ohm gauge, it will show empty way before you actually are empty.

 

Tube type senders are for fuel cells with foam in them. They work fine without the foam too.
I have them @ work 8.5" and 10" deep.
I also have lever senders for 0-90 and 240-33 ohm gauges.
Also fords prior to 1985 used senders with 80 ohms empty and 10 ohms full.
The 0-100 ohm sender would just read full longer than if you used the 0-90 ohm sender that the gauge calls for.

 

I rewound my sender to suit the after market Koso dash, and it read backwards so I flipped the circuit board around inside the sender and it works great.

Some pics are in my build thread.