fuel gauge not working when lights turn on

[Boxchevrolet]

hello i just bought a 83 chevy k10 with a 350 and dual rear tanks. the fuel gauge works when i start the truck but when i turn on the headlights it drops below empty. can anybody tell me what causes this?

[Captkaos]

Start tracing wires, you have a short somewhere.

[hatzie]

Loose cluster ground?


From orbit on my Android.

[zieg85]

While researching that very same problem with my 1985 I found this site.  Mine turned out to be a bad plastic circuit board on the back of the speedometer.  I went to a pick and pull and found a replacement cluster, worked like a charm..

[Irish_Alley]

Zieg I was thinking something along that line. I was thinking the dash bulbs were back feeding into the fuel gauge somehow. But couldn't think how

[frotosride]

My first thought was a burn circuit on the board..

[zieg85]

To further explain the issue I had, when I dimmed the dash lights all the way down with the headlights on the gas gauge would return to working fine.  I could not visually find a burnt spot but a new cluster fixed it right up.  I even found one with a quartz clock and took the additional wiring while I was at it. 

[Irish_Alley]

i was wondering if you could "control" the fuel gauge like that. would it slowly rise to the fuel level in relationship with the dimmer level?

[zieg85]

i was wondering if you could "control" the fuel gauge like that. would it slowly rise to the fuel level in relationship with the dimmer level?

Yes, the gauge was accurate with the lights off or park lights/headlights on, all the way dimmed.  Gave the knob a twist and the gauge went to empty slowly based on how bright the dash lights were at.

[Irish_Alley]

be a nice trick to pull of someone when you want to be stuck and out of gas way out in the woods
and that trick could be played on anyone lol

[zieg85]

be a nice trick to pull of someone when you want to be stuck and out of gas way out in the woods
and that trick could be played on anyone lol

How did I not know where this was headed...

[Irish_Alley]

[Boxchevrolet]

well i replaced the circuit board and the fuel guage still goes below e when i turn on the headlights, now I'm looking for a short or bad ground

[bd]

Loose cluster ground?

Agreed.  There is a poor connection in the I/P or cab ground path.  Clean all of the ground connections from the cluster connector all the way out to the battery.  Verify that all of the factory grounds are in place and making good contact (this means taking them apart, burnishing the terminals and attaching points, and reinstalling so they are tight):  battery-to-engine, battery-to-right frame rail, battery-to-radiator support, back of right cylinder head-to-cab, I/P-to-cab above e-brake pedal.

[Irish_Alley]

Also the cluster pigtail