'00 A6 Alarm System odd behavior

Hi all,
Sometimes after I park the car in the garage the alarm horn will emit a low sound like the alarm is going off even though the car is not locked.
It's noticeable only because the garage is a relatively quiet place. The sound level is 1% of the normal alarm level. Loud enough to hear in the house/garage, but not loud enough to hear when the car is parked outside in the driveway.
If I lock the car, the sound stops and it starts again after I unlock the car.
It occurs mostly when the car and the garage are warm say 80 degrees F or more.
I've scanned using VAG-COM which turns up nothing.
By morning, the sound has stopped. It doesn't run the battery down.
The alarm does work at full volume when activated (i.e. 'unlock door with alarm on' or 'dog barking in car with alarm on' or hit 'panic button').
Any ideas?
Thanks, Glenn
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Are you sure that what you're hearing isn't the fuel tank vent 'breathing'?
--
Peter Bell (Note Spamtrap - To reply, replace 'invalid' with 'bellfamily')

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Hmm. Not sure. How would I know the difference? Perhaps by taking the gas cap off when the noise is occurring?
Glenn Spence
wrote:

'bellfamily')
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wrote:

That'd be a good place to start - though that would leave one wondering why the sound stops when you unlock the car...
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It's supposed to warm up here in the next couple of days so I'll see if it makes the noise and then try the lock-unlock sequence to be certain that they are or are not related. Seems like they are but it has been a week or so since the last event and memories being what they are... Would be a good time to try the gas cap removal to see if that has an effect (engine off of course).
wrote:

the
why
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Follow-up:
Well, it's 94 degrees here and a couple of minutes after I pulled the car into the garage and turned it off the car was making the noise. I tried the lock/unlock sequence which had no effect. I then opened the gas cap and the noise stopped! I can't figure out why I thought it was related to the alarm system but.......
Thanks for the correct analysis.
Glenn
wrote:

'bellfamily')
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