My parasitic draw stopped when I pulled the radio head unit fuse. This is with the car armed and asleep.

Prior to pulling the fuse, neither the head unit or the nav system would turn on.

My guess is there's a draw somewhere in the circuit that would supply power through the radio head unit fuse when the car is off. I'd like to know which components these are so I can try eliminating each one as a cause.

I've looked at many parts catalog and diagrams, but nowhere can I tell what components are on this circuit.

A different question: is the radio head fuse expected to be powered when the car is asleep? I swapped out all the relays 3 at a time but found nothing.

Other thoughts?

2000 XK8 Coupe, 99K miles, premium sound.

 

What year is the car, and is it "premium" or "poverty-spec" audio.
All the wiring diagrams are on Gus's site
JagRepair.com - Jaguar Repair Information Resource

 

I think the radio is typically still powered when the key is in the ignition so you can listen to the radio even with engine off. There is that trap door on the ignition, but if you say it is asleep, then it already closes and works.

Also, if the car is new-to-you, check for any accessory that could feed off the radio wiring. Check under the armrest for a phone device, or a radar detector, etc. Some folks have also found old tracking devices. There is a big all-in-one plug under the armrest that is the perfect place for accessories.

Also check the power antenna circuit. See if it is separate from the radio. Unplug it and see what happens.

At some point, you may have to throw parts at the problem. I can't believe radios for our cars would go for all that much money on eBay. Or pull the radio out and inspect the board for damage.

To be sure, check the wiring diagrams on jagrepair,com. That should be the ultimate answer.

 

Oops, added the car specs above.

I've had the car for about 6 years, everything worked until a few months ago. I was getting low battery issues around then.

I removed the fuse for extending the antenna years ago.

Pulling the amp fuse did not stop the parasitic draw.

On other cars I've had, the radio is switched through the "Acc" accessory position of the key.

I've been over the the wiring diagrams several times but can't find the answers. I suppose I could pull the radio and check resistance.

 

From the wiring diagram, it looks like fuse #9 (10A) in the passenger side fuse box provides a permanent supply to the head unit but not to any other circuits. Fuse #12 (5A) supplies power when the ignition is in the first (accessories) or second (on) positions - this also only goes to the head unit and no other circuits.
But - from the head unit, there are power feeds to stuff like the amplifier and the aerial so when you remove either of those fuses you are also removing power to those "other" parts of the audio system.

 

Long shot - does the antenna extend if you replace F9 in the trunk fusebox with the head unit turned off?