Contact the maker via the inter net,request or download a new booklet.
Check the bell push for water ingress.(Moisture ) dry out
Check that no one near by has installed one and left it on the SAME install frequency.
Is any one arriving near by in the early hours ARMING a car alarm? radio waves do funny things on there travels.
if possible change the code in the bell push and the receiver you have ten thousand to choose from at least.
wirecutterman
April 2009