Why does my A4 beep randomly when parked? 5 min silence, 40 beeps, silent, beeps, etc

[piblondin]

My 2002 B6 A4 suddenly won't shut up when it's parked, and it's starting to cause a problem at work and at home. Can anyone diagnose this issue? Here's what I can tell you:

Last spring the alarm horn in my trunk started to fail--or, at least, I thought it was the horn that was failing. Each time I used the remote to lock the car, the beep got fainter and fainter until it stopped making any noise at all when I locked the car or when I pressed the panic button to start the alarm. This didn't seem like a big deal to me, and I was worried about wrecking the weather seal if I pulled the lining out of the trunk to access the alarm horn box, so I just let it go.

Fast forward to 4 am Monday morning when I hear my car beeping. (The beeping comes from the trunk.) It goes for 40-50 beeps then it stops for 5, 10, maybe 15 minutes and then it starts beeping again. Beeping, silence, beeping, silence. There seems to be no exact pattern to this, and it's been going on ever since when my car is parked. It doesn't seem to make a difference whether I lock the doors with the remote or if I leave them unlocked.

Here's some additional information:

The lights on the car do not flash when the beeping occurs.

It never beeps while the car is on, only when it's off and parked.

If I press the two buttons above the trunk release on the driver's door before I lock the car, the beeping still occurs.

If I unlock the car or open the door or trunk while it's beeping, doing so does not immediately stop the beeping.

When I lock the car with the remote, the red security light on the door flashes quickly, then goes solid for a bit and then blinks as normal.

When I engage the alarm or lock the car from the remote, there is no beeping.

The remote does lock the doors properly.

For the past year or so, the left tweeter (is that the right word for the speaker at the top of the door?) in the driver's door doesn't always work. All controls on the door appear to work correctly.

So, the possibilities I've come up with are:

1) That some of the wires in the driver's side front door wiring harness have become busted. (My car is eight years old--the driver's door has been opened and closed a lot--so that seems possible.)

2) That I've blown a fuse--either #14 or #38.

Beyond that, I'm really not sure. Has anyone else experienced a similar problem? Any other suggestions? Should I go ahead and order a new wiring harness for my door?

Thanks so much for any help!

[A4DJ]

Sounds like your car likes to party.

[rollerton]

I'd scan it first, see if there are any error codes and if they're related to the anti-theft system being set off. I know the interior monitoring system can get quirky with age.
Otherwise my guess is at the beeper itself since dis-arming the system doesn't turn it off right away.

[heywier427]

to me the cars beep and chirp.

a chirp is the alarm arming, and a beep is the horn going off.

i assume your beeping is chirping (to me), and i sounds like the batteries are going bad in your alarm module.

you can search for a diy to get to it, but i dont think anyones fixed the problem without replaceing the whole module. ive found the part #s for the batteries, but i can only find them out side of the us, and theyre always out of stock! most people just unplug it and dont care about hearing the chirp or not.

also, the weatherstripping is no big deal to remove. you cant ruin it unless you really try. so dive in there!

[piblondin]

to me the cars beep and chirp.

a chirp is the alarm arming, and a beep is the horn going off.

i assume your beeping is chirping (to me), and i sounds like the batteries are going bad in your alarm module.

you can search for a diy to get to it, but i dont think anyones fixed the problem without replaceing the whole module. ive found the part #s for the batteries, but i can only find them out side of the us, and theyre always out of stock! most people just unplug it and dont care about hearing the chirp or not.

also, the weatherstripping is no big deal to remove. you cant ruin it unless you really try. so dive in there!

heywier427, indeed, the sound I'm hearing conforms to your definition of a chirp. It's not the name noise that the car makes when I honk the horn. I'll clean out my trunk and see about accessing the alarm module. I figured the batteries were already shot months ago when the panic button stopped making any noise. But, perhaps, that wasn't the case?

[piblondin]

So...this morning when I woke up the beeping had become very faint—and just one beep at a time. This suggested to me that perhaps the problem was in the alarm module and that it's battery was finally, really fading out. HOWEVER, I went out to the car and unlocked it and relocked it with the remote and it beeped upon locking for the first time in months. Then I hit the panic button, and it beeped normally as it also had not in months.

Now, I'm totally confused. I guess there must be a broken/shorted wire somewhere, but where? Thoughts?

Thanks!