2001 VW Beetle Alarm System goes off when locked and parked

SOURCE: Have a 2000 VW Beetle. The alarm won't turn off!

My 2000 Beetle does same thing (although not all the time). Just found an internet post that suggests there is a problem in the door lock sensor. I assume you are using a regular key - not
the keyless entry - like I am. He also said that you can disable the alarm (also disables the
keyless entry - which doesn't bother me) by leaving the front door AND the rear trunk open and
starting the car up. Seems to work so far. I will get the door lock sensor replaced and turn the
alarm system back on (not sure how yet), and let you know if that stops the problem.

SOURCE: 2001 VW Beetle. The driver's front seat adjuster

I'm assuming you have manual adjustment seats. There is a spring underneath the seat that locks the end of the lever into corresponding notches in the seat frame rail. That spring has either fallen off or broken.

SOURCE: disconnecting the factory alarm on a 99 vw beetle

well know you need to take the keys to the dealer ship and have the keys recoded becuse when u disconeded the alarm the code was read by the alarm know you have to recode it hope this helps .if you have a dummy key try it and see if the same thing happens when you turn it on if it does then have keys recoded. hope this helps

SOURCE: VW 2000 New Beetle door sensor/car alarm goes off when doors open.

I found a thread - http://forums.vwvortex.com/zerothread?id=1542461 that details the repair of the soldering on the key lock door module. Our 2000 new beetle had the same issue. Also sometimes it refused to start. Soldering pins fixed it all.

Also see http://forums.vwvortex.com/zerothread?id=1015107 for releasing window from track, And door handle from inner panel.

I ripped the door apart and re-solderd the pins. I only had one pin with cracked solder but two others looked thin so I did them while I was in there. It's about a four or five hour project if you have all the tools. (8mm triple square also called an 8mm internal was the hardest to find - Also needed Torx T8 T10 T15 and T30 plus Philips Screw Driver. )
Project is difficult but not too bad for the mechanically inclined. A 7 on a scale of 10.
Since re-soldering pins - no more issues! My guess is that a VW dealer would get $200 for a new moduel plus 5 hours of service time for this gig - easily a $500 to $1000 bill. My cost - several new tools - about $25.00.

SOURCE: 2001 vw beetle blinkers wont work

One difference here. One the NON-CONVERTABLE new Beetle, the hazard button is the flasher... on the convertable, there is a separate sealed relay box under the dash to keep from having the switch short out of you leave the top up.