I had a new fuel tank put in my 1986 F150 now my fuel gauge dont work.I checked my ground wire it is fine I checked my other wire wich seems to be hot wire.I tested it with a wire tester and it was flashing.I do not know to much on these matters could some one advise me on what could be wrong. Thank you Brenda

 

From your first sentence I would return it to the tank installer for warranty work. Your tests basicly indicates the problem is in the sending unit.