how to disconnect one pir, Accenta6 alarm?

Have you tried using the part sets (PROG) 2 or 3?.

That sensor may have already been programmed for omit in one of the part set suites.

Check:

Pop your code in then press (PROG) then either 1,2,or 3,.1 being the full set or 2 or 3 being part sets,now press (OMIT) then the system will display the zones about to be armed.

Now press the corresponding number of the zone you wish to omit and the zone led will go out,now press (SET).

You have now set the system with that zone omitted.

e manno
July 2013