I am working on a 1951 Chevrolet 3100 Pickup. I do not know the milage. It has the original manual transmission.
The fuel gauge reads past full when I turn the key. I tried tracing the wires, but the wires are a mess right now. What could be wrong?
Fuel gauge (top right, where it says 12V)
I am not sure if the wire on the sending unit is ground or positive, it is a purple/gray wire.
I'd appreciate any input. Thank you.
On most of those old fuel gauges they'll peg past full if there's a short somewhere and they're receiving full voltage instead of reduced voltage through the rheostat in the sending unit. You can test the sending unit by removing it and connecting an ohmmeter between signal and ground, and work it through its range. (Your shop manual should have the resistance range of the sending unit.)
Does the gauge still peg past full if you remove the wire from the sending unit? If so there's a short somewhere in your wiring feeding full voltage to the gauge.
Another thing, as I recall in a previous post that truck now has a 12-volt electrical system. If it originally came with 6 volts, which would be the case for most 1951 vehicles, you need a voltage reducer for your instruments.
Hello again, I just unplugged the wire from the sending unit. It still goes past full. I'll have to rewire the fuel gauge. and go through that wiring mess. Thank you again for the help.
you have 12 volts going into the gauge without a voltage reducer.
but the gauge has "12V" stamped onto it right next to the terminals.
After I posted his gauge picture I noticed that 12V stamped on the back of the gauge too. I deleted my post regarding a voltage reducer
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Good catch, Joe
Yep, I missed that as well, maybe that was installed when the electrical system was converted. There must be a short somewhere between the gauge and the sending unit. (Or the sending unit is shot.)
yeah, @thatolchevy even said, "top right, where it says 12V"
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D'oh! Guess we need stronger reading glasses
Okay, so yesterday I decided to go see where the wire goes to. It went under the seat and connected to nothing. Do I just connect it to the fuel gauge?