1966 b-body fuel level sending unit

Hello, a little confused about my fuel gauge for my 1966 b-body.installed a new sending unit into tank. fuel gauge in dash shows nothing(and yes theres a half a tank),so I checked the gauge in the car,it works,pulled the tank then unit checked on the bench with meter and its right.New wire from gauge to sending unit,new ground strap.The unit was bought from Vans in Wisconsin.Any clue what is the problem?thanks Donnie