My fuel gauge is giving me fits. It has not worked correctly since i got the car 4 years ago. I have done the following:

• Put in a new sending unit
• Checked all of the grounds and other connections
• The gauge works, I can get it to move by unhooking wires.
• Reads just above "E", then when I turn the key to on, it drops below "E"
• If I unhook a ground, the gauge will go way past Full
• Put an ohm meter on the plug in on the harness for the gauge, says 38

I am no wiring guru, it is my weakest area by far.

Question is: the plug in connection that goes into the harness in the trunk has one wire from the the tank plugged into it on one side but nothing on the other. The ground from the tank goes to a direct ground on the steel support that surrounds the filler neck inside the trunk.

Is this right? should there be two wires going into the harness plug? Pic attached.
There's also a ground from the sending unit on the bottom of the car too.





Any help would be great,
Thanks,

 

The tan wire from the sending unit might be grounding out, which will peg the needle below E with the key on, like what yours is doing. As a test, you'd want to run a new wire from the sending unit to the gauge, and bypass the factory tan wire.
The sending unit reads at or near zero ohms with an empty tank, and 90 ohms with a full tank. Your 38 ohm reading means you have a little over 1/3 tank.
Can't say what that second wire on the plug is, what color is it?

 

Fuel tank s/unit ground is on the bottom of the trunk floor, on the pass tank strap mount.
Ground shown is for lights, side markers, if equipped, license plate light, and tail lights.
The other wire is brown for license plate light power.

As you said, you have resistance from connector to the s/unit - good.
As Senior Mod suggests, measure the other connection, the body harness, to ground to see if the wire is crushed somewhere from the connector in the drvr kick panel to the trunk.

As a last resort, go to Radio Shack and get two 50 ohm resistors, anywhere between 45 to 60 ohms will work.
At the body connector, drvr kick panel, tan wire, disconnect connector.
Tan wire into dash harness, connect resistors in line as in series, between ground and the tan wire = full tank
Connect one resistor, same way= approximately half tank,
Connect the resistors in parallel and same way to connector = approximately 1/4 tank.

 

Second wire on the plug is all brown.

Can you get to the back of the fuel gauge without pulling the dash apart?
I can feel on the back of the gauge side of the instrument panel, the turn signal light and other idiot lights.
There are also 2 what feel like are wire terminals but I thought there was supposed to be 3.
I don't feel any wires going to them, are the actual wire terminals inside the gauge housing?
I pulled all of the screws out of the gauge cluster but I can't get the whole package to drop down, do you have to drop the steering column?
I have the gauge sitting at a 1/4 tank until I turn the key on, then it's "E". Does that sound like the ground on the back of the gauge? I would also like to run the wire straight from the plug in the truck to the gauge as you guys suggested but again having trouble figuring out access to the gauge. I definitely can't fit up behind the dash to see since I'm 6'3" 250lbs, hell I barley fit in the car at all, lol.

 

The inst cluster has a 'ribbon' circuit board on the back and the harness connector plugs into it for all the functions seen.
There is a ground wire at the very top center of cluster, but it is ground for all functions, lights, etc., not just the gauge. Later, you can lengthen the ground in aiding not to go back underneath to connect, use star washers for definite ground.
You should be able to pull the cluster to get it out without dropping the column, but it is only two bolts/nuts.

No wires inside the cluster. At the trunk connector, tan wire, one direction should read resistance through the sending unit to ground, 0 ohms, empty, 90 ohms, full.
The other direction, you should read a low voltage from the gauge referenced to ground.

 

I second most of the posts already. I lost ground at the fuel gauge. I just pulled the connector plug and sanded down the ground lug at the back of the gauge. (thee are three lugs). Since I did not want to go through the grief of removing the gauge, I did it with a mirror to find it, them sanded blindly until it looked shiney. Plugged it in and now my gauge works great.

 

had the same problem..
I just did ribbon circuit board and it works now..
it was just three nuts to drop steering and 4 screws for cover..
made it way easier to pull gauge cluster out.. plus I was able to take apart and clean it before puttn back in..

 

Here is a pic of the gauge cluster
There was no ground at the top of the cluster
I ran one from the top center screw before I unplugged the gauges but it didn't make a difference.
There is a light bulb that plugs into the center at the top of the cluster, (what's that for?)
The plug in connections don't look bad.
Maybe the ribbon is bad?

 

slidejob26,
Check out this link, http://www.chevyclassicsclub.com/the...ry-1965-newer/
Terminal A: Fuel sender from the tank (usually a tan wire)
Terminal B: Switched ignition hot (usually a pink wire)
Terminal C: Ground





It looks like you are missing the resistor CG-60 and the connector spades/prongs. The plug connector prongs were rusty on my fuel gage connection. As noted above, I just cleaned them up and my gauge started to work, I am not sure where your ground wire "C" went.

 

The socket at the very top is the high beam indicator.
Be sure to add a ground wire to it also.
A #61 bulb (3 watt) and round socket would work.