Did you ground the wire behind the radio?
There is a wire that has to be grounded or else the alarm will sound. It is designed to ground when the radio is in place. Once you remove it, it will sound the alarm as if someone stole it.
Check it out. It is all the way in the back of the radio compartment. Right down the middle on the bottom part. If it isn't there it might have fallen out of place. It looks like a small clip.
If it doesn't work disconnect the alarm under the passenger footwell, as Benzmac suggested already. It is approximately 2"x6" in size with a white sticker on it. It has two plugs one 12 pin and the other 14, I think.
You probably disconnected something else because there is no way that the alarm can go off if you disconnect the alarm control unit.
[Edited by vinamg on 01-11-2001 at 01:52 AM]