New boy on the site - so please be gentle. I have a 1998 C240 Estate - Elegance and have suffered over the last few days with the alarm going off, apparently at random. I stopped the nuisance alarms by disabling the movement and interior sensor using the button on the dash (fortunately the light keeps flashing so it still looks as if the alarm is on as normal). Having looked at posts on here I assumed that the siren unit had given up the ghost. Today I took the car to a local alarm specialist who has a MB machine and he downloaded the trip-fault readout. It was all internal sensor trips, mainly lhs but also rhs. He also noticed a fresh spider's web in the back of the car. He emailed MB and they replied immediately saying that spiders (and small moths) were a common cause of nuisance alarm-trips and that you had to get rid of them - sometimes even by fumigating the car! Using the software programme he has disabled the interior sensors until I can get rid of the spiders. Funnily enough, I had the car cleaned at the local hand car wash on Monday and the young woman who does the insides screamed when she found two spiders in the front. This all stems from me ferrying garden waste to the recycling centre on Friday and Saturday - you have been warned.