Fuel gauge gone kinda screwy on me

[Ward8121]

I'm new at this, posting, but I've been scanning threads for the past three years for help with my truck.
I hope someone can help. I was working on my truck, 70 cst20, taking out things the previous owner had installed and discovered a new issue. I was installing a new horn and removing the windshield wiper delay as well as a malfunctioning after market ammeter when I noticed my gauges began to move with the key off. When I turn the key on and start the truck everything works fine the gauges go to the proper position, but when I turn the key off the gas gauge goes way past full off scale. Did I clip a ground that I wasn't supposed to? Help please, I don't need to be standing in the street putting out a fire again. Thank you