The only CEMCO print I have is from 2001 and does not have Fire Service in it. On this print the start of the car and hoist way door lock circuit is terminal 36, which is fed from the car and hoist way safety string. The end of the hoist way and car string door lock is terminal 35 and that goes through a n/o contact of PF and feeds input 35 on the plc. According to this print the entire car and hoist way door circuit is between 36 and 35 some where, if your print is like that, start back tracking your locks till you get to the wiring issue. I would assume by your troubleshooting so far some one has put another wire at the end in terminal 35 at the end of it.