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1941 Chevy 1/2 Ton Pickup

Facts:
The truck has been rewired with harnesses from Rhode Island Electric. There is a new gas tank as well as a new sending unit (tested). The guage reads in the reverse. That is, when float is raised the guage will move toward empty. If I ground the sender wire it will move toward full rather than empty as it should.

In desperation, I even reversed the wires on the guage. Nothing changed. Same situation.

I'm at a loss. Need help badly!

Thanks,
Ed

Ed.
See if these articles will help you.
Harold

Thanks for the articles. I did perform the tests covered in the articles. Regardless of what methods I use, the needle will do exactly opposite of what should happen.

In your first posting, you stated that you reversed the wires and got the same results. If you grounded the sender wire to the gauge, the needle should never move. If it did, you've got other problems.

On some of those after market senders you can slide the float bar out and put it in the other side to reverse the action of the resistor.

As a side note if the sender doesn't have a reversible float shaft you can "carefully" bend the float shaft 180 degrees close to the pivot point and accomplish the same effect.

Take the float out of the tank with the wire still connected. Attach a ground wire to the mounting flange (you can use a small bolt and nut to do this). Then move the float up and down while someone monitors the gauge. If it reads full when the float is down, and empty when it's up, and it goes up and down smoothly as you manipulate the float, then you've confirmed that the float is the problem and not something else. Once you've confirmed that, figure out how to reverse the float, as LeeP points out, so that the resistance increases as the gas level increases.

It's a very simple circuit. The flange is grounded, and the wiper bar that moves on the resistor adds resistance to the circuit based on the float level. When the float is in the down position (empty), the wiper bar should be all the way at the bottom (or top, depending upon its design) of the resistor. If, when the float is down, the bar is farthest away from the grounded side, the float needs to be reversed.

Question regarding Harold46 post of fuel gauge testing.
Fuel gauge in 51 Chev. 3100 five window reading full. Question is, if I pull the battery from the vehicle and the issues covered in the fillingstation article exist (bad ground, etc) will the gauge still read full?

Thanks,
Sam
Tex. Chev. 51

If a good gauge/sender is not grounded at the sender, it will read full (if the ignition switch is on and the battery is good).

Run a lead/wire from a sender screw to a good/clean ground, to test the gauge and the quality of the "circuit".

Do you have a 6v or 12v electrical system?

It is a 6 volt system. And yes, I do have a good ground from the sender screw to the frame. Thanks to all that have replied.

Did you ever get this sorted Ed?

He last posted on 12-9-2017.
I am going to guess that whoever manufactured that sending unit, assembled it wrong. Would like to hear back from guys with problems like this.
Maybe he used a sharpie and put an F where the E belongs, and vise-versa like I'd've done. (Take note of the rarely used triple contraction. )
Carl

Could be Carl. I'm having some fuel gauge issues so need to bone up. Nothing is easy to get to. Noticed that Harold posted some pretty good documentation on troubleshooting.