76 Fuel Gauge
Thread Starter
Burning Brakes
Joined: Sep 2002
Posts: 1,009
Likes: 62
From: Houston Tx
I did some more testing and looks like the previous owner or someone did some wiring with the rear light harness. I found that the passenger side rear marker is grounded with the sending unit ground for some reason; That probably explains why my fuel gauge reacts the way it does when the headlight switch is pulled to the "on" position.
Also, there appears to be a break/loose in the ground that goes to the fuel sending unit; The ground wiring is ok from the sending unit ground plug at the tank to the sending unit connector under the rear driver side fender.
My ground problem appears to be upstream of the sending unit/ground connector headed towards/inside the car. Can anyone let me know exactly where the sending unit ground ends up from once it enters the car? I want to ask before I start ripping things apart to trace it.
Thanks
Also, there appears to be a break/loose in the ground that goes to the fuel sending unit; The ground wiring is ok from the sending unit ground plug at the tank to the sending unit connector under the rear driver side fender.
My ground problem appears to be upstream of the sending unit/ground connector headed towards/inside the car. Can anyone let me know exactly where the sending unit ground ends up from once it enters the car? I want to ask before I start ripping things apart to trace it.
Thanks
Last edited by hgoodwiniii; Dec 17, 2019 at 06:56 AM.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,117
From: Crossville TN
Every electrical component (lamp, motor, gauge, etc) has a ground wire, usually terminating at the frame/chassis. The metal chassis then carries electrical ground back to the negative side of the battery....which is connected to the chassis/frame underneath the battery compartment. This works great!...until the ground connections on that frame get corroded/rusted/dirty. Then the problems start. And, sometimes, those ground wires can age and deteriorate inside the insulation...or fracture inside, which will yield an intermittent electrical connection.
Ground feeds likely cause MORE electrical problems than power (12vdc) feeds, as both are equally important to make any electrical device function. And with a Corvette having a plastic (non-conductive) body, grounding is a lot more problematic than with a metal-bodied car.
Ground feeds likely cause MORE electrical problems than power (12vdc) feeds, as both are equally important to make any electrical device function. And with a Corvette having a plastic (non-conductive) body, grounding is a lot more problematic than with a metal-bodied car.
Le Mans Master
Joined: Aug 2006
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From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
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If you followed the Willcox suggestions and it passed all the tests then your gauge ground is good.
The gauge lights going ON when you turn on the parking or headlights tell me the gauge ground is GOOD.
The taillights and the sending unit both ground together near the rear left side frame.
The TAN wire originates at the sending unit and enters the birdcage at the lower left side it goes behind the carpet and under the sill plate and to a 12 point connector that is behind the left kick panel.
Since your gauge works with the headlight switch OFF I guess that all the above is good.
You may have a problem with the sockets for the turn and parking light sockets.
Remove one bulb at a time and check for a good ground at each one.
Let's see if anyone else agrees.
Pete.
The gauge lights going ON when you turn on the parking or headlights tell me the gauge ground is GOOD.
The taillights and the sending unit both ground together near the rear left side frame.
The TAN wire originates at the sending unit and enters the birdcage at the lower left side it goes behind the carpet and under the sill plate and to a 12 point connector that is behind the left kick panel.
Since your gauge works with the headlight switch OFF I guess that all the above is good.
You may have a problem with the sockets for the turn and parking light sockets.
Remove one bulb at a time and check for a good ground at each one.
Let's see if anyone else agrees.
Pete.
Thread Starter
Burning Brakes
Joined: Sep 2002
Posts: 1,009
Likes: 62
From: Houston Tx
I believe I finally figured this out; Somehow, the fuel sending unit ground circuit was not getting any ground flow. I confirmed there were not breaks in any wires in the fuel sending unit neg or ohms wires. The only thing I could come up with is that I painted my fuel tank and used those tank anti-skid pads between the tank and the chassis when I reinstalled it. I believe either the painted surface or the anti-skid pads is preventing the tank from getting a negative charge from the chassis. I corrected the problem by running a negative directly to the chassis and the fuel sender negative wire.
