I have a 1972 Chevy 3/4 ton with the gas tank behind the seat. Just before going on vacation the gauge read properly. The day I am leaving the gauge drops from what I know I have in the tank to about empty. The gauge does move a little when the gas slushes around in the tank. I fill the tank and the gauge pegged at empty. As I use gas it starts to move again.

I put in a new dash panel and repainted the gas gauge needle. I pulled the needle the first time I worked on the panel and was off a little in my readings so I redid it. I was having a problem getting it back to ready correctly until I set the needle to full and replugged in the power connection to the panel. It worked that way for about a year.

Would it be possible to disconnect the battery and use a magnet to position the needle and reconnect the battery and have it read correctly or is there another prceedure for setting the needle? I am guessing that becasue it does move the sensor in the tank is working.

Any suggestion would be appreciated.

Just from reading this two or three times, I would think it is a problem with the windings on the tank sender.

There is a flat strip with fine wire wrapped around it. Then the contact point on the swinging arm rubs on a particular part of those windings. It is possible that at some different gas levels, that they are not making a good contact.

You could test that theory by keeping an ohmmeter hooked up to the sender while slowly filling the tank. (disconnect the wire, and test the sender only).


Or, take the sender out and manually work it slowly to see if the ohmmeter shows some bad spots.

take the wire off at gas tank , jumper wire it to good ground , if it moves the Gage , its your sender .
but check to see if tank is grounded first ,it lies in rubber strips and bolted in , rust or corrosion .
ohm meter it to check for ground .
you could also jump tank to good ground first , to see if gage rises to your known fuel level .