Monteey

Old c type so is likely to be quite old

Hmm cant say ive ever heard of a pre wired system have you checked the programming to ensure that zone 1 hasnt been isolated accidently

I suggest you get your multimeter out and make sure your getting a closed/open signal from the pir when you trigger it, also you need to make sure the zones not used on the panel are linked out. Afraid im not familiar with the above unit so not sure if it is possible to program zones as not used without having to link them out, but linking is always the safest way.