Fuel gauge stops working with headlights on.

[Bogey]

I recently picked up my first corvair. 1965 monza convertible. Fuel gauge seems to work fine until i turn on the headlights. Once i turn them on, the fuel gauge drops to empty. As soon as i turn the lights off, the fuel gauge functions normally. Not sure where i should start. Thanks!

[davemotohead]

Start By checking your grounds,check the one that comes off the fuel sending unit and screws to the body panel under the car at the gas tank,if you have bad grounds,things will get whacky!

[mcgasman]

Its gotta be a ground problem..

[Bogey]

Thanks for suggesting grounds. I'm still trying to learn my way around the mecanicals. I have the shop manual and some other manuals, but I'm struggling with finding all of the grounds.

It gets more wierd as it looks more like a ground issue. The fuel gauge stops working when the headlights and dash lights are on. If I dim the dash lights all the way down, the fuel gauge works again. I also can get it to toggle working when i click on/off the high beams.

I did find and visually inspect the ground that comes off the fuel sending unit under the car and it looked good.

Is there a list somewhere that describes or shows the location of all of the grounds?

What is the most reliable way to test the grounds?

Also, should my fuel gauge continue to display the actual fuel level after the car is turned off? Mine does continue to read actual level, unless I turn on the headlights with dash lights, or click the high beams.

[Bogey]

Does anyone have a picture of the physical wiring behind the dash?

Are there any ground wires back there?

I will pull my dash if i know there are ground wires back there.

Thank you!

[bbodie52]

The plastic 1965 and later Monza and Corsa instrument clusters rely on metal straps to ground all of the instruments. These metal grounding straps tie to the metal chassis frame at one point (shown below), and if the connection is loose or corroded, the instruments may display some strange behavior.

[Outlaw]

Poor ground on the dash is a very common problem. Took me days on my LM to figure it....had all kinds of quirky problems going on.

[Bogey]

Problem fixed! There was a phillips head screw on the bottom of the dash that included the ground strap exactly where the posted diagram showed. It was a little loose. Once I tightened that up, all dash functions started working. Thanks for everyone's great advice.

-Ed

[JCrane1]

I registered to this site to simply say THANK YOU. I recently bought a 67 Corvair and was experiencing the same problem. I just finished replacing the headlight switch in attempts to fix the problem. I then found this post and discover the screw was missing in the ground strap location. I installed a screw and fixed the ground problem. All the gauges are now working perfectly. Thanks very much guys!!!

[cad-kid]

I registered to this site to simply say THANK YOU. I recently bought a 67 Corvair and was experiencing the same problem. I just finished replacing the headlight switch in attempts to fix the problem. I then found this post and discover the screw was missing in the ground strap location. I installed a screw and fixed the ground problem. All the gauges are now working perfectly. Thanks very much guys!!!

Excellent Please stick around and introduce yourself. Photos of your vair would be cool as well

Welcome!

[BobWitt]

I wonder if the fuel level would have changed with the back lighting intensity?? Interesting failure mode!

[Bogey]

In my case, the backlighting did not work at all without the ground screw intact. Fuel level only responded while light switch was in off position.