Hi, my new to me XJR has a plate in the front ashtray with a 3.5mm audio input socket and a on/off rocker switch. Hopefully the photos are attached.
Any ideas if/how I get this to work with my oem hifi?
I have the CD/CDC/AM/FM unit and I cannot seem to find the signal from an MP3 player connected to this socket (although the AM radio does get more suppression when the switch is on).
Should I just take the lot apart and see where it is connected to?

 

It's probably running via FM Modulator. Mine is set to 89.1. I set a radio preset to 89.1 and flip the switch. With a Belkin CarAudio Connect, I use it for music and my phone calls.

I would turn the switch on, plug in your device and play something, then manually tune the FM radio until I found the right frequency.

 

Finally looked into this this morning. Comes through on FM 87.9 when phone is connected to it and the power button is on.
Sounds pretty good to me, not muffled or distorted. I am happy, but likely to look into the BT option in the future.

 

Looks interesting! FM modulator is certainly a 'simple' way of getting an AUX input...

You might want to head back to the XJ ( X308 ) XJ8 / XJR - Jaguar Forums - Jaguar Enthusiasts Forum subforum, there have been quite a few discussions about audio recently, which you might find interesting.
The threads there seem to end up being more useful, and X308 specific, than the threads in here