Rear Window Defroster In/Op

[Botbasher]

So as the days have turned colder, I have started to use features of the car that had remained dormant.

It appears that my rear window defroster doesn't work. Wondering if there are any common issues that can cause a fault or testing options?

I have checked:

Button on A/C panel lights up when pressed.

Relay in the Pass Side panel in the trunk was swapped for a similar one. Could hear relay click when installed in other socket... no click when installed in the Defroster socket.

Have wandered through OBD11 looking for an output test to manually but cannot find where it can be manually operated. Gateway... Central Electrics...???


Since the switch lights up and the relay doesn't click, I am leaning towards a module, but which one and before diving in that deep are there other options??

Cheers,

KS

[Valpo A7]

Check at the window defrost elements to see if you have power to them. Speculating that you could be able to use 1 of those non contact voltage testers to see if there is power going to them. It is not uncommon to break a line on the window.

Do you have access to a service manual? Should be diagrams in that to help chase the wiring and module locations.

[Botbasher]

Check at the window defrost elements to see if you have power to them. Speculating that you could be able to use 1 of those non contact voltage testers to see if there is power going to them. It is not uncommon to break a line on the window.

Do you have access to a service manual? Should be diagrams in that to help chase the wiring and module locations.

Unfortunately non-contact testers only work with AC voltages... and generally only 110v and above, so to test it means a good ole voltmeter and removing some panels... and it's the removing panels I am trying to limit or avoid!

I have the wiring diagram, and it was a little helpful... it says that the power goes through 2 antenna/filters before being used to heat the window. Which makes no sense with the shark fin on the roof?!? Does anyone know where these filters are in relation to the relay or rear window array?

Was hoping that there might be a common fault/failure or defined test method that might limit the destruction. It seems to be the only thing on the car that you cannot function test... or maybe it has some obscure name that just doesn't make sense.

Trim panels have a way of never going back just the same way they start and this car is still 99% unmolested, so there are no creaks, rattles or buzzes... yet!

Still hopeful there is an easy way, but preparing for the drama of the normal way!

Cheers,

KS

[AudiInMyA7]

Following because i have also noticed that my rear defroster is also not working!


Sent from my iPhone using Audizine Forum

[gk1]

When they removed my rear window to repaint after my sunroof explosion the rear defroster was also not working.
It was something to do with the grounding wires not connected properly on the passenger's side I believe.
That being said, if your rear window has never been removed then I doubt that would be the issue and I would start with the fuses.
I believe if one line in the window breaks, that just that one line doesn't work, but the rest still will. BTW the lines can be tested directly with a plain continuity tester without removing panels if you so desire.
In my case, with a bad ground, the button led lit and the relay clicked, it just did not heat the window elements.
FYI it was $1500 to fix at the dealer (paid by the collision shop who did the paint work because they couldn't figure out what was wrong.)

[Botbasher]

In my case, with a bad ground, the button led lit and the relay clicked, it just did not heat the window elements.

Since the relay doesn't click at all I am on the other side of the problem... control line. Just need to find out where they start and end!

Cheers,

KS

[Botbasher]

So this is what I have for a wiring diagram. J393 is the Convenience System Central Control Unit. Since the relay isn't clicking, I presume that the failure is an output issue or a failure between it and the relay.

I have scanned all the listings in the Convienience module but see no direct way to function test the relay. IDid I miss it? Is it named something funny? Is it under a different module?

I'll physically check it if I must, does anyone know where that module is? So much less frustrating when you don't have to needlessly tear the car apart!

It is the only thing that I found doesn't function on the vehicle. Guess it could have been worse!

Cheers!

KS

Rear Window.jpg

[Valpo A7]

This link might help.

https://www.kolhosniki.ru/elsaonline...tm#id804001007

[Botbasher]

This link might help.

https://www.kolhosniki.ru/elsaonline...tm#id804001007

Helps quite a bit... after I ID it, I'll just need to shrink my freakishly large hands down to fit through the little hole to get at it!!!

Appreciate it!

Cheers,

KS

[Botbasher]

For record and those that follow... Here is the Fuse and Relay location on a 2014 S6.

Rear Defroster Fuse and Relay.jpg

Got the relay to click in the socket yesterday, so it might be a bad relay or socket... the investigation continues!

Cheers,

KS