We just acquired our 2007 XJ8L VDP. We have '04,'05,'06 and this '07 so we are familiar with the balance control on the audio dash consul.
This car has had a Sirius satellite radio installed in where ashtray was. This may be the root of the issue. A 1" square box (I am guessing it maybe Sirius antenna?) mounted on the roof above rear window. I don't know how it works or if it does, and furthermore we really don't have any desire for Sirius so it could go.
The Jaguar's factory radio is not picking up local stations very well. Maybe screwed up because of the Sirius. However, one 'audio specialist' I spoke with said, "on Jags that their is a part of the audio system that causes the reception to go out and the rear speakers to fail; and they fail first... its a replaceable part located in the trunk; $100 to try to diagnose", he said.
Does this make any sense? What part is it? If this is so?
I suppose the consul needs to be opened to see what and how Sirius is connected. Perhaps the antenna wire is not connected? But the speakers not connected too?
I found a YouTube video on how to open the consul, remove the radio.
Does anyone have a schematic of the Audio System?
Any help is appreciated.
Gina Anderson - Blessed with a Jag addiction!
'03 Ford Expedition
'04 XJ8 - young adult son's daily driver
'05 XJ8L Vanden Plas - my daily driver
'06 XJ8L Vanden Plas - hubby's injured car; being rebuilt
'07 XJ8L Vanden Plas - hubby's new daily driver

 

Read my post "Need factory Sirus help". The same issue. I never went any further, as I think it ended up to be an internal issue with the Sirus switching box located in the boot after checking all the connections including the ant conection in the rear c-post. I disconected the power from the box and have great FM again (no sirius). After that, I installed the greatest Jag assy EVER. The BT unit, talked about on the forum. Replacing the switching box didnt make sense with the BT unit available.
I'm not missing anything about not having the Sirius unit other than, Crappy sound, and the bill every month. Now I just have to pull the head unit when I find an ashtray that will match the rest of the wood.

 

Silly question, but have you powered off the Sirius module before trying to listen to local radio? If the XM is on, it is switching off the FM antenna so it can inject its signal.

That said, if it still doesn't work and you don't want XM, I'd pull it. Even when it's working it reduces the FM signal on an already marginal radio system. I discarded the complete XM system from my car when I first boguht it. If you pull the radio out there is an RF modulator and switchbox in series with the antenna input to the radio. Remove this and you should have perfect reception again (barring any issue with your radio or antenna itself). You can remove the rest of the XM system at your leisure.

As far as the rear speakers affecting the reception, sounds like BS to me. On a stock Alpine system the only part in the trunk is the audio power amp, and it's not $100. There is an antenna power coupler behind the C pillar, but the radio is all contained in the dash unit otherwise.