Hello all. I hope someone has an idea about my problem.
I just bought a 1968 SS. Car just completed a resto. A new wiring harness was put on firewall forward. However, there are some bugs it seems.
When I apply brakes the gas guage goes from E to F and beyond. Let off and it goes back to E. When the lights are turned on the green arrows for the turn signals are illuminated and stay on. Turn signals still work though.

I am unable to see a ground cable on the frame or firewall or engine. does that sound like my problem?

Thanks for the help.

Does the gas gauge do the same thing when you step on the brake while the car is not moving? You might just have a loose wire at the sending unit on the tank. Also your turn signal switch might be grounding out somewhere causing a complete circuit. Check your flashers for the turn signal and for the hazards at the fuse box. Replace the one at the fuse box first and see if that helps.

Definately possible - ground problems will cause all sorts of freaky things like this to happen. At a minimum, you need the battery (-) connected to the block and battery (-) connected to the driver's side fender. Also, on the instrument cluster, there is a metal strap that should be grounded to the top center screw of the cluster. This ground is tied into the high beam indicator. There is a specific order of assembly - I'd recommend a search to be certain you get the right info.

Car just completed a resto.
As above poor grounds provide weird things.
And is coomon after a resto/paint due to grounds under dash, lights, consol etc having been painted or over sprayed.
Blowing light bulbs, high temp readings, false gas level readings, weird stuff like u have are signs of bad earths

Definatly check that middle ground screw in the instrument cluster. It boggled me for weeks, causing all sorts of gremlins with the panel and lights until I finally tracked it down.

Thanks for the info. I drove the car late this evening and here is exactly what it was doing.
Push brake pedal, at anytime, gas guage goes to full.
Turn lights on, turn signal lights on dask come one.
Interior lights not working nor is i nterior dome light.

thanks again for the info. It will give a place to start.
Lb

ya, i swear i was having that turn lights on and signals would come on problem with that missing ground screw in the middle.. check it out and possibly tighten.. good luck.

U got a full wiring diagarm?

for a 67.. not a 68.. check under my website.