Hi all...

2004 XJ8 here...

Yesterday I get in the car to run an errand, and when I start it up, there's a LOUD sound from my rear speakers. Remember 'the most annoying sound in the world' from Dumb & Dumber?

https://www.youtube.com/watch?v=0cVlTeIATBs

Sounded like that 'emergency broadcast system' tone, just a few octaves lower.

Yeah, it sounded a lot like that. I fiddled with the stereo to no avail. I could actually hear my music/radio if I turned it up, so the stereo was still working...

Anyway, the sound stopped after about a minute and I chalked it up to some weird glitch.

This morning, when I'm about to head off to work, I put the key in, and... dead battery. Had to call a coworker for a ride

Obviously I've developed some sort of weird electrical issue. Does this sound like anything anyone here has experienced? Any pointers? Could this sort of thing just be a sign of a failing battery (I know weird stuff happens when batteries start to fail sometimes... )

I'm going to pick up a trickle charger for the battery on my way home tonight so I'm not stranded again tomorrow.

 

So a battery test at Advanced Auto Parts says the battery is good, and the alternator seems to be good as well.

I trickle charged the battery overnight last night, and it started up fine and got me to work this morning. However, the battery was too low to start the car again today. When I turn the key, I hear a brief crackle from the rear speakers.

I think it's clear that something is shorted. Is anyone familiar with these symptoms? Any troubleshooting tips? I own a multimeter. Any idea how I can go about identifying what specifically is drawing current from the battery? I can't get my car to a mechanic until this weekend at the soonest. I'm going to trickle charge the battery every night, and disconnect the negative battery cable while I'm work, for now...

 

Well, for anyone experiencing something similar - turns out the issue was a fused circuit in the amplifier that caused it to draw 5 amps of power even when the car was off. Replacement of the amplifier was the cure.