Is the transformer in the plug?
If it is you will need to get creative.
If it is not you are not doing something right
On a lighter socket the center nipple is + and the outer is ground.
Hope this helps.


A local shop can find an appropriate + hot wire for you.
Wrapping around a fuse is not a good move on electronic controlled cars.
I am not talking down to you I just don't know your experience level.
Let us know how it goes.