[usmcmuel]

my 1972 chevy c10's fuel gauge is not working it just sits on e i have no idea wear to start i suck at electrical work

[75gmck25]

Is your tank still in the cab?

Start out at the tank
- Make sure the sending unit has a ground wire and that it is properly grounded
- Find the other sending unit wire that runs up to the gauge. The stock wire should be tan.
- When you turn on the truck there should be 12 volts on that tan wire. If there is not, then you need to trace it back and find out where it is disconnected.

If the wire coming from the dash has 12 volts, but the gauge does not work, then you probably have a bad sending unit. If you disconnect the sending unit wires from the tank (you will just have the two terminals on the tank) and measure resistance between the ground connection and the connection for the sending unit wire, it should vary from 0-90 ohms as the float moves up and down in the tank.
However, its usually a broken wire that causes the problem.

Bruce

[usmcmuel]

yea its still in the cab and ill try all that thanks ill let you know how it works out USMC CPL MUELLER

[usmcmuel]

ok i found the brown wire that come from the top of the tank and i traced it and no breaks in the wire

[alittle1]

Try studying this diagram http://www.crankshaftcoalition.com/w...iring_diagrams

[75gmck25]

Is there a junction or terminal where you can disconnect the brown wire from the sending unit?

- You need to disconnect the brown wire from the tank, turn on the ignition, and then put a voltmeter between this wire and a good ground. With the ignition on you should measure battery voltage (about 12 volts). If you don't get 12 volts, you need to check the fuse for the tank circuit. You must have 12 volts coming from the dash.

- Then use the multimeter set on resistance to verify that the sending unit ground wire and terminal is actually grounded (meter should show 0 if you put one lead on sending unit ground and one lead on a ground in the cab or on the frame).

If both of the above checks are successful, then turn the ignition on and connect a small jumper wire between the sending unit wire and ground (with the wire still disconnected from the sending unit). This will apply a full 12 volts directly to the gauge and the gauge should go full scale to empty.

Now make the same check as above, but instead of the jumper wire use a small resistor between the values of 0 and 90 ohms. Radio shack still carries a 10 ohm resistor in a two pack, and you might find some others in the audio section of a parts store. All you need is some values that will let you verify the gauge works when you add resistance into the circuit.

If you make it this far and determine the gauge works, then its probably the sending unit that is bad. However, I would first take it out and stick it down into a full can of gasoline and let it soak. Then move the float back and forth to make sure it floats up and down and moves correctly. If its only the floating part that is bad, you can try to find something to replace it. However, the new float must "float" in gas and it must resist gasoline. About the only predictable choice is the float out of a junked gas tank.

Another check - As you move the float on the sending unit up and down it should change resistance from 0 -90 ohms. However, its also possible that the electrical part of the sending unit is bad, which means the only choice is to replace the entire sending unit.

Bruce