Heated rear screeen not working

'93 110 CSW: heated rear window / screen hasn't worked since I bought the car last year.*

Checked fuse OK, switch OK (I think - surprised to find 3 terminals, but it changes resistance enough when switched...) element appears to be OK (continuity good).

I then had a look at the Haynes wiring diagram and noticed there was a relay and a diode in the circuit. Where are these located and which components are the most likely to fail on a Defender?

(Bit of a bummer while removing the switch panel. No extra force used, but as I pulled the panel forward the hazard warning switch 'exploded' in a shower of bits, leaving the front half in the panel and the back half connected to the loom! Discovered that the indicators won't work if I remove the switch remains from the connector, so I've left it in place. New switch now on order...)

check the earth connected to the rear door first! mine had fallen off!

Sensible suggestion, but will the rear wiper work if this is the case?

(The rear wiper DOES work!)

From what I can remember, dont shot me..........there are three wires (earth)all linked into one terminal behind the door card. Also the positive wire runs through the rear door and that can corrode. So, check condition of both wire going to the element first, then the earth

for quickness, create a new earth for the element to the chassis to see if that sorts the problem first before you start ripping the rear door to pieces.

Thanks. I'd expect to see + volts on at least one of the terminals, and possibly both if there's no earth. Don't think I've checked this yet (can't remember: it was a couple of weeks ago now, and it was getting too dark to keep playing! - besides, I was more worried about my exploded hazard switch!)