I would use a voltmeter, turn on the ignition and touch the leads one at a time. Ground the negative lead of your voltmeter, and touch the posts on the back of the gauge. One will read 12 volts. That is your hot lead. The other one is your sender. Does that make sense?

Deve

1950 Chevy 3100 Deluxe Cab
1950 Chevy 3100 Standard Cab
In the Stovebolt Gallery
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