Does your front door have a door contact fitted that would normally start an entry timer as you open it?
If there is the contact has stuck closed, as the door was closed still.
The contact needs to be replaced or, if it has corrected by now it will only happen again.
Maplin or an electrical wholesaler that sells alarm equipment.
If your battery is more than 5 years old get a new one as you are there.
The good luck man., May 2017
