Hi
You should have a siren unit somewhere under the bonnet. The key will be for that as it'll go spastic if you pull the battery off and its not been turned off with they key. Its possible the CL has something to do this but you'll need to find the alarm control unit and tell us all what it is. Only one I've seen used on a disco so far is a Sigma, but then I've only really grubbed around one Disco