Heated rear screen & door mirrors not working

[tonupkid]

Hi Bex
My D3 HRW was not working either, apart from just 2cm across the top.
I could see that the black edging down the OS side of the screen had delaminated.
Audi confirmed that this was the problem, so I asked them nicely to put it past their warranty people, and to my surprise they replaced the screen with a £325 contribution from me.
My car has done 95k and is 6 this year, can't complain.
Incidentally, I think the elements are inside the screen and can't be damaged by scratching.
Perhaps this is a known fault, have a word with your dealer.
Good luck

Oh yes, my mirrors weren't working either, not sure they do now

[A8L Chick]

Originally Posted by snapdragon

I'm not so sure it is the window itself as each element is in parallel, so if one was damaged, it would only affect that line rather than all of them.
The main ones at the sides are too robust to be damaged in normal use.
According to the SSP287_035 PDF, "The Central Control Module for Comfort System actuates the heated rear window over the Rear Window Defogger Relay J9. The relay activation information is supplied to the Central Control Module for Comfort System by the Climatronic Control Module."

Looks like CC panel sends a message via CANBUS to the Central Control Module and that sends juice to the J9 relay.
see page 45, but the relay output goes through C18 radio interference suppressor on the way, so maybe that is duff!
https://dl.dropbox.com/u/1273965/A8L...Components.pdf
https://dl.dropbox.com/u/1273965/A8%20fuses-pred-d3.doc (see p.17 for fuse and relay location if you haven't got that far)

Good luck

Thanks for all inputs so far guys, and I will possibly put this to audi

However, it may be a massive co-incidence, but when I have my lights on, I am noticing allot more interference through the radio than normal. Being a biker, I always have my lights on..

I wonder where this part is located?? Could this be the culpret.

Yes it's the whole screen that is currently faulty-not a single line of demist

[A8L Chick]

I still have no heated mirrors or rear screen. God do I miss them in winter... I cannot fathom this issue

[snapdragon]

The mirrors and window don't look associated on the wiring diagram.
Here are the rear window fuse and relay.
If you turn on the rear window, does the LED on the switch stay on?
Does it affect DAB or FM reception?

[HPsauce]

Originally Posted by A8L Chick

I still have no heated mirrors

Whenever I've had heated mirror issues I've always done a couple of simple electrical checks:
Take the offending mirror off and check for voltage (12V or so) on the connectors and check the resistance of the mirror between terminals.

I'd expect the resistance to be under 10 ohms. Much higher and it won't take enough power to warm up much.

As it happens it's always turned out to be failed mirror(s), on several cars including my old S8 (newer one is OK at present, though the heated rear window is quite "slow").

My S8 mirrors are nuclear-powered though - they start steaming in seconds!

[A8L Chick]

Originally Posted by snapdragon

The mirrors and window don't look associated on the wiring diagram.
Here are the rear window fuse and relay.
If you turn on the rear window, does the LED on the switch stay on?
Does it affect DAB or FM reception?

I don't understand how they can't be associated when they are activated by the same button?

Fuse is fine and relay replaced

Light stays on and doesn't seem to affect reception

Ruddy cars! lol

Originally Posted by HPsauce

Whenever I've had heated mirror issues I've always done a couple of simple electrical checks:
Take the offending mirror off and check for voltage (12V or so) on the connectors and check the resistance of the mirror between terminals.

I'd expect the resistance to be under 10 ohms. Much higher and it won't take enough power to warm up much.

As it happens it's always turned out to be failed mirror(s), on several cars including my old S8 (newer one is OK at present, though the heated rear window is quite "slow").

My S8 mirrors are nuclear-powered though - they start steaming in seconds!

My Mirrors were always amazing also...thats why I miss them so much.

I'll check for power-not thought of that. (DOH-Blonde!)

[A8L Chick]

WOOOOO HOOOOOO

Guys I forgot to say that this problem is fixed!

I do feel rather stupid though... it was the connection behind the drivers side mirror.

So I wiggled the wires and voila, it started heating up! As did the rear screen and the n/s mirror.

This was all on Christmas evening.. Best xmas pressy I got

I have a feeling that the mirror had received a hard enough clump from someone to make a poor connection... what a shame I didn't check this sooner! I literally checked everything else!

[Delboy]

That's got to be the luckiest find ever, how the wiring behind the mirroe effects the rear demist is a strange one.

[tc4332]

Well done Bex.
Give that Gal a big prezzy.
This is the odd ball sort of thing that makes A8 ownership so interesting.
Have to keep this one warm for future reference.

[M-A8]

Score....but a weird one, well done