Hi Everyone,
I have just bought an 2004 Audi A4 2.5tdi and it is affected by the same problem as my previous 2 Audi's, and from what I read on here other owners cars as well:

Radio works fine normally, but when rear demister is switched on reception is vastly reduced or replaced with white noise (hiss) this may cut in and out (as on my A6's) or be permanent until demister is turned off (as per my A4)

Firstly, does anyone know what the problem is? These cars (A4,A6) all have the antennas built into the windscreen (saloon models not sure about advant which may have bee sting style antenna) and from memory an inline booster that boosts the signal and isolates the radio electrically from the antenna- so is it the booster at fault? or is it the antenna it self shorting with the heater element in the screen?

I'd be interested in any user experience, if you had the problem:-

Did it do it from new?
Did it start intermittent then continuous when you operated the rear demister?
Have you had any part replaced that has cured the problem?
Did your reception degrade in anyway with the demister turned off?

I spoken to an Audi dealer and they werenot helpful, I told them I've had it on 3 cars so it must be fairly common, they denied this and said they can book it in for investigation by the hour, and replace the booster etc which is a bit of a fob off.

So I'd be interested in your comments and hopefully can get to the bottom of what the problem is and how to fix it. If this ground has already been covered,- can you point me to the post?

Thanks!

Wayne

 

Following up my own post, after extensive googling, one theory is that the power from the heating element is using dirt to track across the glass to the antenna and upsetting the booster.
The solution is to clean the glass with a proper glass cleaner, and it seems to help if the element is on.

I have done this and its certainly improved things, but its not perfect, still interested if anyone has noticed this problem from new, of this helps anyone.

Thanks