Heated rear windscreen fault

[guysy]

Hi,

I am new to the Audi world, I have a 1.4tfsi 2010 A3 and I'm working through the small niggles as I find them.

As its got colder I have realised the rear screen demister does not work at all. I am questioning weather the heated wing mirrors are as well but I *think* they are ok. I am going to put a multi meter across the terminals at some point.

Going back to the rear screen I have had the boot lid cover out to try and fix the issue, no tabs are broken on the element wiring, the fuse is fine. So I am trying to rule  out if its the "antenna booster" module, pics below. It seems the heated screen power wires go into this unit, the 2 right black blocks seem to be left and right. 

Can anyone shed some light on this for me? is it likely to be a failed unit, or do they rarely fail?

I need to do some more investigating, I also need to check the switch although that lights up when pressed and stays on for its timing.

 

Thanks

 

 

 

 

[Magnet]

Hello Guy,

I too would be treating the continuity test on the screen element as the first test. If the element has a ding in it (often due to putting something high in the boot and closing the glass against it) then pulling anything else apart will be to no avail. Obviously disconnect the terminals first. If that is OK then simply work back from there, checking for 12v where 12 volts should be. 

If the element tests show it to be OK, then it might be worth checking the harness in the flexible section where it feeds from the body into the tailgate - often a source of potential problems since the wiring can become brittle due to temperature and continued flexing.

Kind regards,

Gareth,

[guysy]

Hi, thanks for the reply.

Sorry I forgot to mention I had the boot hinge rubbers down and the wires looked clean both sides with no cracking etc.

I have just turned the engine on, pressed the rear screen button, it lights up as normal, this time I have taken the right wing mirror glass out (as I have read the heated wing mirrors work with the rear screen switch on) and there doesn't seem to be any voltage going through them.

All internal fuses seem fine I have checked them.

Could it be a relay issue? I see they are behind the interior fuse box and a pain to get to without unscrewing the fuse box?

Would there be any fuses in the engine bay that control the heated screen / mirrors? Ive given them a look over and they all seem intact. 

 

Thanks.

[guysy]

I see the heated rear screen switch itself is incorporated into the climate control unit, and not a separate switch (I had it in my head that the switch was on a lower panel separate to the climate control unit but it isn't.

I will remove the head unit tomorrow and check all of the plugs are in the climate control properly.

Sadly I don't have a VCDS scanner available, I am planning to purchase OBDeleven as I've heard its fairly good?

Does anyone know if any of these (im guessing the 2 smaller if any) is the relay for the heated rear?

 

Thanks.

 

 

 

 

 

[Neil Dickinsin]

My A6 heated mirrors work with the front demist and the door arm rest switch on either mirror position not the centre top position. 

Edited November 19, 2018 by Neil Dickinsin

[guysy]

Thanks for the reply, this time before I went out I listened for a relay click, Im not sure if it was there before but I pushed all relays in a bit earlier, and there is definitely a click now... 

And some success, not sure if its all working but definitely had warm working mirrors this time. I need to wait till it mists up or get a kettle out and check if its solved the rear screen. 

I will report back. Cheers.

[cliffcoggin]

Guy.

Spare yourself the guesswork and the trial & error. Use your multimeter to test for power and continuity at the element. If those tests fail, work backwards from the screen.

[Redbreast]

Hi, i have a 2010 A3 cabriolet with the wires on the rear heated screen have been pulled of the glass, by the plastic surround bonded to the glass that hold the headlining, the dealer says i have to replace the entire roof at a cost of nearly £3.000 anyone got any ideas for a cheaper fix, Robin

[cliffcoggin]

Try conductive paint. I have no idea how effective it is but you have nothing to lose.