My alarm sys. in my '87 TD was acting up, actually it would stop. Under the carpeting on the passenger side, you will find a large black plastic cover. With this removed you will find 2 connectors, one of them is for the airbag, leave that one alone. The other is for the alarm. Some have said that a battery that is getting old will cause this problem. I know that the battery in my TD is 4 years old and should be replaced. I haven't done that yet, and put the alarm back together to see if that was indeed the problem.
1994 MB E320 Coupe (199,500 mi)
1992 MB 190E 2.6 (173,000 mi)
1983 Porsche 911SC (148,000 mi)
2004 Volvo V70 2.5T (198,000 mi)
President of CT/Westchester Section