Helping someone with a heated rear window problem.
Switch has three circuits involved:-
a) the lighting circuit which passes through the switch.
ii) the little circuit which controls the on/off HRW tell tale lamp which is protected by a 7.5A fuse
3) the main circuit which activates the heated rear window relay.
The relay itself is mounted on a small panel above the in-cabin fuse box, behind the dashboard, and is a small cube about an inch square. From there the feed travels down the passenger side of the car and up the B pillar to a connector to the rear window.
Sometimes the connectors where the wires attach to the rear screen fractures, these can be re-soldered on, or re-attached using electrically conductive glue. You can buy electrically conductive glue or you can make your own by filing down a steel bolt and then mixing those filings into a 2 part epoxy glue such as Araldite to make a very metallicly paste. you need a lot more filings than you may think.