1996 Vanden Plas
I've searched the posts for this with no luck so far so I ask for advice on this one.

My alarm will sound about 30 seconds after locking doors. After locking and re-locking several times checking to insure all doors and trunk were securely closed I discovered that:
1) After depressing the locking button on the key fob, the sounder announces the car is locked and security is engaged. 30 seconds later the alarm sounds - shuts off properly with the open button on the fob.

2) Then I lock the car again, same steps, and after the normal lock/alarm beep, I get a single short chirp. (It is the same sound one gets if a door or the trunk is not closed.) If I get this new tone, oddly, the alarm does not sound.

Of course, the alarm "misfire," and that second chirp upon second lock attempt are the puzzles here.

The first thing I did, of course, was check to make sure all the doors and trunk were closed tightly. Then I replaced the battery in the fob.

No change.

I was going to try our second fob, but that one seems to be temporarily misplaced.

Note: I should add that this happened on the first sunny day after a couple weeks of drizzle and a day or two of pretty heavy, constant rain. It has had plenty of sun and time to dry out though if that had anything to do with this issue.

Before I take it to the dealership for expensive diagnostics, I am hoping someone here has had a similar experience.

Thanks for your expertise,
Tom