Fuel gauge slowly climbs past half tank

I have a 1968 cougar base model

Tested good replacement gauge, new sending unit, new voltage regulator, new wire to sending unit

Tank is empty and the gauge slowly climbs past 1/2 tank

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Is it a rebuilt original sending unit, or an aftermarket reproduction (like ACP)?

The aftermarket units are typically not OEM quality or calibration.

XR7G428 / Desert Classics can help.

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You should send the gas gauge and gas sending unit to Bill Basore for testing and calibration. One of them is off. While you are at it, test the Instrument Voltage Regulator for output voltage. The reproductions are crap so don’t simply replace it - test the voltage.

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It is a original tested gauge from west coast classic cougars

What is ment by “ new wire to sending unit”? Is this wire outside of the original wiring harnesse, how long, and to where?

I said ‘sender’ and you said ‘gauge’.

I would start with the unit in the tank, the sender.

Unless the temp gauge is doing the same thing you can eliminate the Instrument Voltage Regulator from the picture. The first thing to do is to use a multi meter and measure the resistance from the sender out put to the sender mounting flange. With an empty tank the sender should measure greater than 60 ohms. Anything other than that and you need to pull the sender and see what is going on.

I had the voltage regulator wired wrong. After looking at the wiring diagram I was able to correct my mistake and run new wires outside of the original harness and the gauge is spot on reading correctly

Thank you for the update. Good job figuring it out. Stupid electricity