not sure how it's doing it but as you said probably have to pull the dash & see where/how the orange wire dash light circuit is bleeding over to the fuel gauge circuit & in the meantime I'd disable the dash light orange wire circuit to avoid any damage tho you'd think if it was permantntly damaging it it'd have done it by now but never hurts to be cautious. I'd drop the column a bit then drape a rag over the column to protect it then pull the dash (remove a batt cable first)