logic development..

[altafjamadar]

Hi! everyone
i am beginer of s7-300 and undertraining on plc programing
but i found dificulty to modification a logic on funnace control

in this we needs to conrol air blower
when we start furnace air blower should on.
our temp reach o to 1200 .
aftr finish our production we switch of furnace
but that air blower should on up to 800 deg after it will off.

thanks
jamadar.