2001 Transit heated front screen?

Hi Ive fitted a new front heated screen but my van had no headed screen, so ive fitted the switch and 2 relays, and that part works the relay clicks ans the switch lights up, how ever the wire from the screen that plugs in to the cable in the van pillers end in the foot well nearside is a gray plug with 3 wires and offside a black plug with 2 wires that come from the screen, where or what should the pluge fit to or where should thay go to?? can you please help?