1990 thunderbird sc alarm problems on 1990 Ford Thunderbird SC

My thunderbird has the keypad entry on it. When i lock the doors the alarm sets, a minute or so later the alarm goes off. I have to keep it inlocked for now. How do you reset the alarm? Am I doin something wrong?

Asked by for the 1990 Ford Thunderbird SC
Mine is the same, if all doors are shut and I lock it with the key pad the alarm does not go off
1 more answer
you might have a bad door ajar switch that is triggering the alarm.