sup,i had just fix my rear window defroster. the problem was that one side did was not plug in and the wire was missing. i had to get a female plug to hook it up along with a speaker wire and connect that part to a ground. this ground is connected to the same ground on the other end( the rear window have to plug, left and right) THIS IS THE PROBLEM… my rear defroster works now 
but the problem is that only the top half is defrost and the bottom have is not … does anyway know why? could it be the ground ??? :hmm: i know this is long but thanks for your time
some of the lines might have been broken, check for breaks in the conductors.