I have an 05 S-Type R with Nav. When I have the radio on, I have perfect reception until I turn the rear defroster on.

Does anyone know what's going on?

 

Does your S have a rear window radio antenna? Uneducated guess would be a short between the rear window defroster and the antenna - coupling DC into the radio's front end when the defroster's turned on.

 

It was one of those strange electrical "gremlins" that only did it that day. I don't have my windows tinted so isn't a factor. I just hope it won't do it again.

 

Iluv, I know this is going to sound silly, but look under the window trim on the C-pillar (between the rear doors and the rear window) on the left side. You should see a small module there on the pillar. Follow the black wire to where it attaches to the body of the car. There should be a second wire there (if you follow it, it should go to your rear defroster). Loosen this connection, clean up the terminals to get rid of any stuff that may be there and then tighten it down really good. That should correct your problem.

 

That one from Thermo is a good one. In fact check all grounding screws are tight that may be associated with the power to the demist element or the radio aerial esp. if its one of those metalizations in the rear screen itself. We don't know how the demister element is powered -- it may not be simply connected to the +12volt supply with a switch. It may have an electronic power regulator (of the pulse-width-modulation type) to limit the current. It may be switched on and off by the computer, after a command from you. If it has such an electronic power supply, failing electrolytic capacitors can cause radiation of r.f. energy at a frequency of (commonly) 150KHz. If it only happens now and then when demisting, I shouldn't lose any sleep over it. There are worse things afflicting cars...
Leedsman.