The previous owner installed a radar detector that previously only detected 25 mph signs and airports but has recently started beeping almost constantly. It's time to find and remove it.

My first guess is: behind the stereo. I'm open to theories at this point but in the meantime, are there any good How To videos or instructions on how to remove a radio from a pre-facelift XJ-S?

 

Pull off the aircon knobs each side
This reveals two threaded rings round the aircon knob spindles that hold the aircon facia onto the dash
These have to be unscrewed using a special tool or fab up something to do it
Pull off the aircon facia carefully as there are fibre optic lines that are attached to it very precariously
This reveals the radio, which can then be pulled out once the gimcrack tin holding bits are released.

Personally, I think it more likely the unit you seek is under the dash, as there is no room in the radio slot for extra bits. Maybe undo the lower dash (shin level) panels and look there first?
Greg

 

Thanks for that.

I found it wadded up behind the driver's side under scuttle, on the other side of the steering column from the fuse box. It was wired into the fuse box but because the fuse box has no slack, it's hard to tilt it back and see where the power lead is connected. The fuse for the driver's side lumbar pump is overrated at 15 amps (passenger is 5, both sides work) so I'm guessing that's it but I can't easily get at it so I put a wire nut for automotive purposes around the now snipped power lead and taped it up so it won't easily come off.

Anyway, thanks again for the insights.