How can disable an alarm on a 97 deville?

Take off the inside door panel and see if there is something by the lock that activates/deactivates the alarm when you turn the key. Compare the drivers side(L), to the passenger side(R), that works. All mechanical things like to break down over time.

get the fob checked at a dealer as this sends random signals to the ign system as part of the alarm/anti theft systems ,if ign system not getting signal the anti theft system thinks cars being stolen ,using correct key in ign lets you dive vehicle but you may be storing up more problems the longer you leave it

Not positive if it works on VW's but try locking/ unlocking the passenger door with the key. There are sensors in both doors.

Insert the key into the door lock on the driver side and move it to the unlock position two times quickly. That should turn off the alarm.

will your key work in the passengers side?
If so I asume you have electric door locks. open drivers door from inside shut the passengers door. go around to the drivers side shut the door lock the doors from inside then unlock the doors open door shut door and try to start it...as far as disableing it you will have to take it to nissan electrical tec.

lock and unlock drivers side door with the key will disable the alarm system

Try this: open the driver's door (or whatever you have to do) to get the alarm to go off (activate) . Then, while it is honking the horn or doing whatever it does , walk around the car to the front passenger door and using your door key turn the lock cylinder to the lock and then unlock position . I believe this will disable the alarm system if it is a factory installed OEM alarm .

try turning the key on then taking the +side off then turn key off and reconect+

try unlocking driver's or passenger's door with key..you also may have a broken wire under driver's door sill plate..trim by driver's seat

I had same problem, when a door lock broke, the car thinks it has been broken into once the alarm goes off. Mine started going off randomly when this lock broke. You have to reset the alarm system, with my 1990 Acura it was reset finally by putting key in door lock and turning key back and forth 3X. In my car, it was OK to do the key in door lock cycle in the passenger side door lock, but Acura dealer told me not all Acuras will reset it via passenger side key cycling, some require driver door lock key cycling only. I was lucky since my driver side door lock was currently useless, that my car allowed it to be done by key cycle on pass. door lock. But try that and if it doesn't fix it, just call acura dealerships until someone tells you the right answer. In my situation it took 3 dealerships with 3 different answers until this was the right one for my 1990 Legend.

PS I was told you can't disable alarm since it is all integrated into the battery and starting system, but read on another post that someone disableld theirs by disconnecting the horn.