Needing fuel gauge help!

[match71gmc4x4]

Fuel gauge reads way past full and never moves! I have tried another sending unit (brown) wire, but it did not change anything, still reads way past full. Anybody got any suggestions, is it a grounding problem?
I know, I have seen a thread about this before, but I can't find it now.

[JimKshortstep4x4]

Did you try grounding the brown wire from the tank? Gauge should read empty when the wire is grounded. If it does then problem is in your sender or the tank is not grounded.

Jim

[match71gmc4x4]

Any other thought's or idea's on fuel gauge?

[Bowtie67]

Actually if I remember right because I just installed all new guages and wiring in the truck and before I had hooked up the wiring my sender read empty. You can disconnect the wire from the tank unit and see where it is and if it is still reading full I would say a short in wiring, you could also clip the wire as close to the sending unit as possible leaving room to be able to reconnect wire after and try running new wire to tank. Or instead of clipping wire use an ohm meter between gauge wire (disconnected) to body with the wire also disconnected from sending unit and see if there is a short, if no short check wire with ohm meter to make sure its not broken.

[68C15]

use a digital meter & check for voltage on wire at sending unit with wire disconnected. if no voltage it is possible the guage may be open circuit or has no power from ign. sw. or printed board at back of cluster is bad. I memory serves me right the way it works is low resistance-low reading, high res.-high reading(open circuit). will double check later this morn.

[Longhorn Man]

there is no voltage on that wire, it works on an Ohm to ground reading. That brown wire is either grounded out somewhere, or is an open circuit. I can't remember which does what, but that is probably the problem...slide your seat forwats, and trace that wire all the way to the fuse box, I'll bet money that it is damaged under the door sill plate.

[68C15]

I just double checked. the way it works is current comes from the ign. sw to cluster circuit board, to guage, to fuse box, to sender going under drivers side of carpet. wire at sender should have approximately 5V. there is a flat film resistor on back of guage which lowers voltage so needle doest bounce when fuel sloshes in tank. trust me, I have been down this road before on quite a few customers cars & trucks. PM me if you want a wiring diagram. I get them from Mitchell at work.

[Bill72BB]

It's been awhile since I messed with the fuel gauge as I remember , If the Brown wire is removed or broken the gauge will read past full .
If you try grounding the Brown wire and the gauge is still past full ,mostlikely the wire is broke or not connected . As others have said trace the wire under the door sill see if it's open.

Good luck.

[match71gmc4x4]

Ok, I had a friend of mine check the brown wire with his omh meter and it seems to be working fine. My friend thinks that it might be the printed ciruit, we going to change it out tomorrow or Tuesday with an extra that I have to see if that is the problem. I will let you all know how it turns out. Thanks to everyone that replied.

[match71gmc4x4]

My fuel gauage is fixed :p
It was the printed circuit, after changing them everything works fine now.

[match71gmc4x4]

Fuel gauge is working now, but it seems to jump around now, in-between 1/4 and 1/2 (like it will read 1/4 full then jumps around to read near 1/2 full, back and forth while driving, when it is stopped it will read one constant level). I have not filled the truck up since I got the guage working again. Could it be the float is bad? Anyone got any ideas what is wrong?

[thisolechevy]

it sounds like your film resistor is messed up on your circuit, or you do not have one. Most likely the miss readings is your fuel slushing around, so no your float would not be bad.

[toddtheodd]

So that's how to stop that? Check a resistor? I've been ignoring the "dancing needle" for more than a year now. Where can I get this resistor? What does it take to put it on?