just having a heated windscreen fitted after my wife kindly smashed my old one ...(long story ! ...close the door slowly dear !!!! Bang !)
and was wondering what switching gear I will need ?
Does anyone have a wiring diagram I could use please ???
Any comments welcomed !!
Bill.......Lost In France

 

Year of truck? Would need to look in the electrical diagram for that year.

Here is a plan for the Discovery 2, which illustrates that the body control unit engages a relay to switch current thru two 40 amp fuses to the wind screens. The BCU most likely keeps tabs on temperature and how long screen stays on, etc. Point is that you just can't flip on a switch and leave the windscreen cooking all day.

If you never had heated windscreen you may need programming as well as relays, etc.

 

Found this wiring diagram for a 2002 and up Defender front screen, does have a timing module, which also depends on engine being running (oil switch at earth) to engage the timed heater.